I want to make sure these sentences are correct because they will be shown up quite often during my Anki review. I want to make sure these sentences are correct because they will show up quite often during my Anki review.

I am kind of a serious student of English writing ;) I am kind of a serious student of English ;)

It wasn't wrong, but are you ONLY studying English writing?

Reinforcement learning seems to be like training an autonomous car. Reinforcement learning seems to be like training an autonomous car.

Reinforcement learning seemis like training an autonomous car. Reinforcement learning is like training an autonomous car.

In contrast to supervised learning, it may not necessarily require a priori labels. In contrast to supervised learning, it may not necessarily require a priori labels.

This may be correct, I just don't know what you mean by "a prior labels". Grammatically the sentence is fine!

When can "hair" can be used as an uncountable noun and when can it be used as a countable one? When can "hair" be used as an uncountable noun and when can it be used as a countable one?

It sounds better for some reason to be repetitive in this sentence. You could also say "When can 'hair' be used as an uncountable noun or as a countable one?"

I’ve never given it much thought. I’ve never given it much thought.

A few more: "I don't have a strong feeling either way" or "I could go with either / any of those options" or "Whatever you choose/decide is fine with me" or "I would need to know more before I could form an opinion" depending on the context.

I’ve never haven't given it much thought. I haven't given it much thought.

I suppose so. I suppose so.

A lot of these are fine, but I would need to see a sentence that they come after. "Exactly" and "for sure" are used when you agree with someone's opinion. The task you mentioned originally seems more formal than that, but it might just be a formal statement used in a textbook.

What do you do? What do you do?

Another one: "What do you do for a living?"

two pairs of trousers two pairs of trousers

Pants in American English

downpour, rain, shower, storm downpour, rain, shower, storm

' downpour', 'shower' and 'storm' are countable typically. "We had many storms this season with many showers and torrential downpours"

Traveling from an adjacent neighboring country, I needed a piece of advice about accommodation where I wouldwhere to store my baggage and luggage. Traveling from a neighboring country, I needed advice about where to store my baggage and luggage.

"baggage and luggage" is redundant. I know you said not to change it, but as it stands no one would talk like this. Also, "accommodation" makes no sense in this context.

I read the local news to get information on my future work for buying daily bread, although progress was slow. I read the local news to get information on my future work for buying daily bread, although progress was slow.

the phrase "daily bread" here is odd.

I read local news to get information on my future work for buying daily bread, although progress was slow. (I don't really know what you mean here.) I read local news to get information on my future work for buying daily bread, although progress was slow. (I don't really know what you mean here.)

Theseis would be typical behavior of foreigners. This would be typical behavior of foreigners.

I had to utilize all my previous knowledge, perform field research searching for helpful evidence, and do lots of homework within a limited and permitted time. I had to utilize all my previous knowledge, perform field research searching for helpful evidence, and do lots of homework within a limited time.