How to say in Czech: How good is their Slovak?

English
How good is
Czech
Jak dobře umějí slovensky?
Their Slovak is getting better.
Their Slovak is very good.
How do you say that in Slovak?
I do not speak Slovak very well.
You speak Slovak very well.
Their native language is Slovak.
Are they learning Slovak on their own?
He is learning Slovak.
He is not Slovak.
He is Slovak.

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