Though we Weekends

Title capitalization rules. Talking about the weekend in general, we wouldn't pluralize it (weekends)

2 weeks that I can'tI haven't been able to write anything there, for two weeks because I dohaven't have ad time, not only for practicing English, but also for sleeping.

Edited the beginning for a natural structure. Numbers under ten are typically spelled out (stylistic preference)

Usually, I'm working on the evening shift (4pm-1am) b. But some days, I made an extra time work, for examplework overtime, for example, working for 18 hours.

Describing what you are doing now = I'm working
Describing what you do generally or habitually = I work

Working past your normal contracted work hours is referred to as "overtime"

So yeah, I will try to come back, with my badly written text. :)

Though we Weekends

I think you meant to say 'the' weekends. Also we capitalize all words in a title.

2It has been two weeks that I can't write anything there, because I don't have a time, not only for practicing English, but also for sleeping.

You need to specify what about two weeks? Also we write out the word forms for numbers one-nine (1-9).

Usually I'm working on the evening shift (4pm-1am) but some days I made an extra time workwork overtime, for example, 18 hours.

Some days is two words. You also usually need a comma after saying 'for example'.

So yeah I will try to come back, with my badpoorly written text :)

When we're describing a piece of writing, you can say 'badly' or 'poorly'. This is an adverb (word to describe a verb) so it would be BADLY or POORLY rather than BAD or POOR (these describe nouns)