Writing essays could be a really challenging task for non-native students, especially when a reading list is given by experts in their field.

You would say “writing an essay” or “writing essays” here. Either one works, and there isn’t really any clear difference between the two.

That list could be impossibly long, and if theone’s/a student’s reading skillability is not excellent, it can take a long time.

Adding the comma is optional. To me, it feels like it kind of emphasises the idea expressed in both of the sections.

You can choose between “one’s” and “a student’s”. There’s not really any massive difference between the two except for how it sounds. You would just need to choose one of the two because “the reading skill” is a little unclear (but with common sense and context it’s easily understood anyway).

I think “ability” would probably be the more common choice here. Something that I searched up which might be accurate:
“Ability” = how someone does something, or their capability (good or bad) in a certain area.
“Skill” = if someone does something well.

Several recsoursces that students can use for writing academic texts are:/include Google Scholar, Scopus, Web of Science, Wikipedia, academic journals, books, and even online podcasts.

“Recourse” = help in a difficult situation
“Resource” = something that one may use
Those are very general definitions, but the point is that “resources” would be the more likely choice.

You could use “include” or “are”, and it doesn’t really change much.

It’s optional to remove the colon. I believe it was used correctly, but it isn’t really necessary here.

The comma before the “and” is kind of highly debated. I think it’s called an Oxford comma, and it’s useful for clarifying that the things around “and” are separate things (here, it shows that “books” and “online podcasts” are separate things and not grouped together). It doesn’t really matter much here, but I will admit that sometimes it does avoid a lot of confusion by using it (even though I’m guilty of not really consistently using it).
I probably won’t be adding it in to any other sentences here, but you can keep it in mind if you want.

For example, electronic libraries provide an indication of how respected books, theses, abstracts and articles are.

Everything else is plural, so it would be better to make “article” plural as well. Otherwise you could say “how respected a book, thesis, abstract or article is”, where the indefinite article (“a”) applies to each of the following nouns (even though with “abstract” and “article”, it would technically be “an”). You would change “and” to “or” here because you’re only referring to a specific thing in one of those categories, and “and” would imply that you’re talking about one from each category (which could technically be right but feels like a very weird wording to use regardless).

Since you use “how respected…”, you’re saying the degree to which something IS respected. So you would need the “are” (or “is”, depending on which option you choose).

Wikipedia can be a good starting point for in case if a(the) case (that) the subject of an essay is unknown(/unfamiliar?).

I’ve only ever heard “starting point”, but I guess there’s a chance that “start point” could exist as well.

If you wanted to use “for”, it would probably be simplest to say something like “for when the subject of an essay is unknown”.

Otherwise, if you want to use “in case”, you could either say “in the case that the subject…” or “in case the subject…”. I believe there would be little to no difference between the two.

“A subject of essay” would sound like you’re saying “an essay topic” (which I’d say sounds more natural). “An essay topic” would also work.

Otherwise, it would probably sound better to add in an article before “essay”. However, regardless of which one you choose, it would sound like you’re saying that there are multiple possible subjects for the same essay, which is highly unlikely in the type of essay you seem to be describing (the more well known, formal type). Because of this, I’d say that there’s a singular subject (“the”) for one, non-specific essay (“an”).

(Don’t worry too much about this next part)
That could be possible in a discursive essay though, which is more like a discussion on a certain topic, and doesn’t really require as much research because there are so many different ways that you could approach the topic (some might focus more on personal stories (or ‘anecdotes’), while others may focus on humour, or research, or even a combination of everything).

I think “unfamiliar” might be a slightly better choice (though, admittedly, not the absolute best choice).
“Unknown” suggests that the topic wasn’t given at all, and that someone has to think of their own topic. However, in my experience, some idea (even if it’s really general) is always given, likely through a question. It’s also kind of confusing how Wikipedia would be able to help if you don’t have any idea whatsoever of what the subject is (which is suggested by “unknown”).
A different word such as “unfamiliar” or even “uncertain” would imply that someone knows what the topic is, but maybe isn’t so confident with it or sure of what to write, in which case Wikipedia could help (to a certain degree).

EAn essential point is asking other learners who took the course at lastthe year before/in the previous year, because they could provide useful recommendations/advice.

You would need to use an article with “essential point”. Since this is just one (of likely many) essential points, you would add “an”.

“An essential point” also feels a little weird to me (although I’m not really sure why because it does make sense and is a good choice of wording). Personally, I’d probably say something like “a key idea/point”, although that may be a little less formal.

You wouldn’t say “at” with a year. You would say “in”, or sometimes you can also just not use any preposition at all.

Just saying “last year” does make sense, but it feels like you’d be talking about the year before you wrote this.

Then with other wording choices, “last” feels a little confusing, which is why I changed it.
So you could say something like “the year before” or “(in) the previous year”. With the first example, using “in” would sound really unnatural.
But in the second one, it would sound ok both with and without “in”.

You wouldn’t really limit what someone might do, give, etc. to a singular item, such as with “recommendation”. So you would choose the plural.
Alternatively, “advice” would also work.

It is important to define which/decide which (types of) material iss are relevant to the essay, that approachas it reduces the reading time.

I think that “define” is good, but it would be limited purely to formal situations (you wouldn’t really say “define” like that in an everyday conversation). “Decide” could be used regardless.

It would be better to use a plural (and thus also “are”) because there would be multiple things that are relevant.

I think “material” is ok, but it just feels a little weird and confusing here. If you meant deciding what type of resource would be relevant (e.g. books, websites, podcasts), I think “types of” might be better. The problem is that most materials in this context can be relevant to just about any topic if you find the right resources.
However, if you meant specific things from those categories (e.g. which specific books, websites or podcasts would be relevant), I think changing it to “resources” would be better.

You should have an article before “essay”. “The essay” because it’s a specific essay, referring to the hypothetical essay that you are giving tips on how to write/gather information for.

I think “that approach” would sound better as “which”. However, since you use “which” earlier in the sentence, it would feel very repetitive. So you could either change the first one to “what” (“what materials are relevant…”), or change the second one to “as it” as suggested above. Using “as it” is also good because it adds detail as to why it is important to do so.

OIt is, of course, it would be good if students (can) determine which authors are experts in their academic field and what materials are authoritativccurate and reliable.

“Of course, it would be good” sounds like you’re saying that the preferable event would be that students are able to determine those things, HOWEVER they are unable to (which is implied through the use of “would” - conditional?). This would also imply that you would add in what they do instead, due to their lack of ability to actually determine the above things.

Because of this, I’d change “would be” to “is” (to indicate that, at least in some cases, students are able to do so).

It’s optional to add in “can”.

I also prefer how it sounds with “of course” in that positioning here, but you could still use it at the beginning of the sentence and it would be fine.

You would need to use something before “academic field”. “An” wouldn’t be the best choice because it would suggest that it’s ok to use, for example, the work of someone who’s an expert in art for an essay in history (so basically someone who’s an expert in any random area). Because of this, “the” or “their” would be better. While “their”, when you think about it really deeply, could have the same implication as “an”, it doesn’t from a more general view and I think it would be the better choice here since you’re talking in a general sense.
“Experts in the academic field” also just sounds weird, so if this was a specific event, then you’d just say “expert in (academic area)”. For example “expert in history”, if the academic area that is being concentrated on is history.

“Authoritative” is good, but it’s not really used all that often. I think something like “accurate” is the more common choice.

Understanding how information is relevant is one of the keys to success; therefore checking the date when booksomething/a book/an article was published is necessary.

You would use an indefinite article before “book” or “article” here because you’re not talking about a specific one.

However, it would be better to use something that encompasses every type of resource (and for lack of a better word than “resource”, which has already been repeated a few times, I just chose “something”). But you could just say “a resource”.

Several recsourses that students can use for writing academic texts are: Google Scholar, Scopus, Web of Science, Wikipedia, academic journals, books and even online podcasts.

1. In English, the word you are looking for is "resources."
2. When writing a list, only use a colon (:) if you have a complete sentence already. "Several resourses ... texts are" is not a complete sentence, so you do not need any symbol. Ex. "I have visited three countries: Canada, the US, and Mexico. Some languages that people use in these countries are French, English, and Spanish."

Wikipedia can be a good starting point for in case ifwhen a subject of essay is unknown.

Small changes to sound more natural

Essential point is asking other learners who took the course at last year, because they could provide useful recommendation.

- We say, "[do something] last year," no need to add "at last year."

It is important to define which material is relevant to essay, that approach reduces the reading time.¶
To reduce the reading time, it is important to define which material is relevant to the essay.¶

1. Since we are talking about the essay we want to write, you can use "the."
2. I changed the clause order to make it sound natural, but there are many different ways to do it.

Of course, it would be good if students determine which authors are experts in their academic field and what materials are authoritative and reliable.

Small changes to sound more natural

Understanding how information is relevant is one of the keys to success;, therefore checking the date when book was published is necessary.

Because the clause " therefore ... is necessary" is not considered a full sentence on its own, you can use the comma (,) instead of semicolon (;).