I didn't know I would come back here because this is hard for me right now but it's ok.

because is a connecter to connect 2 or more sentences together. There is an independent clause and a dependant clause. Dependant clause are sentences that dont make sense by themselves. They need to be connected to an independent clause, which is a sentence that makes sense by itself. FOR EXAMPLE- i didn't know i would come back here (is the independent clause) AND this is hard for me now (is a dependant clause because it doesn't make sense by itself) To make it more natural we add because so that the two sentences will be together and make more sense.

Bi didnt know i would come back here because this is hard for me nowright now but it's ok.

because is a connecter to connect 2 or more sentences together. There is an independent clause and a dependant clause. Dependant clause are sentences that don't make sense by themselves. They need to be connected to an independent clause, which is a sentence that makes sense by itself. FOR EXAMPLE- I didn't know I would come back here (is the independent clause) AND this is hard for me now (is a dependant clause because it doesn't make sense by itself) To make it more natural we add because so that the two sentences will be together and make more sense. In this case i also added the word right- because you're talking in the present tense so you say right now so that people will understand how you are feeling.

Bbut, it's ok.

I removed the comma because since there is the word because which I mentioned was a sentence connecter you could add it on to the previous sentence you wrote (I didn't know I would come back here because this is hard for me right now)

but it's ok, I will get it.

In this case you can use a comma, since these sentences are both dependent clauses which wouldn't naturally stand by themselves and it makes more sense for a comma (to pause for a second) instead of a sentence connecter like because.

Today is Wednesday andwhich is the middle of the week.

I addeed the word which because its stating the noun mentioned before (Wednesday) a fact or a statement (the middle of the week). I added the word is-after the word which because the word is means to direct and tell us what the statement or fact is.

I live in İstanbul and Istanbul is very hot now.

You could write which is instead of writing Istanbul so that it sounds more natural but you're doing great!

I am feeling tired myself.

You can remove the myself because you already mentioned the subject/ topic which is the word I.

Because I don't have any tasks today so I will drink coffee now which will be nice.

this is good but you can a sentence connecter like the word- so following with the sentence i will drink coffee now to this sentence to make it more natural. FOR EXAMPLE- Because I don't have any tasks today so I will drink coffee now. You can also add it will be nice- because it doesn't sound natural and the sentence is a dependant clause so you can add another comma. Replace the it with which because we already mentioned the topic which (coffee) and which is directing the noun to a statement (will be nice).

Today is Wednesday and, the middle of the week.

I live in İstanbul and Istanbul is very hot right now.

I am feeling tired myself.

I didn't know if I would come back here.

Today is Wednesday and the middle of the week.