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

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

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