How Can I Express ?

How Can I Express Appreciation?

When thankfully I'm corrected my English mistakes are corrected by someone, I usually express my appreciation only.

I'd recommend using something else than "only," it doesn't make sense in this situation.

I know the phrases "I got it" and "I understand," understood but are these right and polite?

Punctuation always goes inside the quotation marks, unless you list a number or letter.

and Can I say it in any other way?

Don't put a space between the word and the question mark.

Could you teach me these expressions?

Again, don't put spaces between the question mark and word.