Can someone check a couple of phrases?

Hi.

I have only a tiny smattering of Classical Greek so I need someone to check accuracy for me. Also, I don’t know where to find Greek characters so I’m doing this in the Roman alphabet. Apologies for that.

I need to know if the following phrases work.

peri tinos dialegetai? - what is he talking about?

ouk epistamai - I don’t know.

ara dunasai romaizein? - can you speak Latin?

ti? - what?

It looks OK.

Gratias tibi do.