[AmgedIsmail]

What if I mentioned the subject in all the statements that include a subject to make it simple for me and for those who I will teach Japanese in the future?

The sentence.
I understand Japanese.
I am going to mention the subject so can I say?

watashi wa Nihongo ga wakarimasu.
わたしはにほんごがわかります。

Do you understand Japanese?
I know that I can say.
Nihongo ga wakarimasuka.
にほんごがわかりますか。

But, if I wanted to mention the subject (You) Can I just say?
anata wa Nihongo ga wakarimasuka.
あなたはにほんごがわかりますか。