My main experience was to understanding how web works, also i had improved my knowledge about the/none MySQL database.
I am confused about the sentence on top. Or correctly i use past time, and about article before titles of something. Also for me it sentence not looks very well, i feel something wrong with it.
There are several changes that should be made in your sentence in order for it to be grammatically correct:
Your sentence is actually two complete thoughts separated by a comma, which is incorrect. The comma should be a period, and "also" should be capitalized.
The use of "to understanding" is incorrect. Instead of "to" I would suggest "in" or "with", though I'm not positive which is best.
You need to include an article in front of web. In this case, "the" makes the most sense: "understanding how the web works".
I don't think "had improved" is the correct tense with the context of the first sentence, and I think just "Also, I improved my knowledge…" sounds more correct.
I am not sure what "the/none" is for, as "none MySQL database" does not make sense. It would probably sound better to make the word "database" plural and remove the article altogether: "…my knowledge about MySQL databases."
So in summary, here is how I would rewrite your sentence to be grammatically correct:
My main experience was in understanding how the web works. Also, I improved my knowledge about MySQL databases.
