[Distortedshell]

Again I am not sure but ga is topic matter. From my Japanese lessons with my former tutor I think it should be o instead of ga. I know I argued about o instead of ga like crazy. I don't know if that is correct though there are many things I am still confused about and this is definitely one of those. But I do think it's:

watashi wa Nihongo o wakarimasu

and

Anata wa Nihongo o wakarimasu ka?

If I am wrong I am wrong. I still try.