How to say in Czech: How good is his Greek?

English
How good is
Czech
Jak dobře umí řecky?
His Greek is getting better.
His Greek is very good.
How do you say that in Greek?
I do not speak Greek very well.
You speak Greek very well.
His native language is Greek.
Is he learning Greek on his own?
Greek is a difficult language.
Greek is difficult.
He is learning Greek.

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