りかいできますよ。(I understand) もんだいありません(no problem) またなにか書いてください(write something again)

It's almost perfect! I have only a few things to tell. にほんご を べんきょう しほす､ ->にほんごを　べんきょうしています I'm studying Japanese. でも､まだ じょうず じゃ ない です｡ -> This sentence is fine. As Oliver-san says, using じょうずですto refer to oneself sounds too confident or arrogant in Japanese context. So, when you want to say "I'm good at....," とくいですis a good alternative. However, using じょうずじゃないです(not good at) about oneself is no problem. Also, for Oliver-san, the negative form of　とくいですis とくいじゃないです, not とくくないです. It's one of the tricky na-adjectives like きれいです, きらいです:) わたし の いちばん すきなじゅぎょう えいご は です。 ->わたしの　いちばん　すきな　じゅぎょうは　えいごです。 Ya, it should be typo, I guess:) ひま で ともだち と むかえります。 -> "I'm free, so I chat(or play?) with friends." Is this what you meant?

it's pretty good! Just the part about not being good at Japanese should change a little I think.. You use じょうず when talking about other people's abilities. When talking about your own you should use とくい。 (or to say not good at, use とくくないです。 And I think you made a typing error and put wa in the wrong place in the second to last line. btw, what does むかえります　mean? Is it like あそぶ？