Currently I'm in Belarus and life is smuch slower.

The mMost of my time I devote to cC and funny sScratch projects.

"C" and "Scratch" as the names of specific programming languages, have their first letter capitalised.

Of course in C, that's the only letter :)

I suspect that life in my pastrevious country made me depressed.

Bit by bit my depression is deisisappearing.

On the other hand, I came back to my birthplace and this may be the reason why I feel better.

CI'm currently I'm in Belarus, and life is such slower here.

* Starting with a sentence with "Currently" isn't a grammatically wrong, but I think it sounds too strong unless you want to emphasize the timing.
* The present tense "I'm" already implies "now", "currently".

I feel serenitye.

Or "I feel a sense of serenity."

The mMost of my time I devote to cC programming and funny s Scratch projects.

* I'm guessing you mean "C programming" by "c".
* I'm also guessing you mean the Scratch platform by "scratch".
* "funny" means смешной, whereas "fun" means весёлый. "fun" seems more appropriate here... unless you actually laugh while doing the projects. :)

AThe feeling of calmness is atypic is unusual for me.

"The feeling of calm" or "A sense of calm" sounds more natural to me.

I suspect that life in my pastrevious country made me depressed.

* "past" describes time, so "my past country" is incorrect.
* "my previous country" or "my former country" or "the country I used to live in" all work.

On the other hand, I came back to my birthplace and this may be the reason why I feel better.

* "the reason why" is redundant.
* Either "this may be the reason I feel better" or "this may be why I feel better" sounds more natural.