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

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

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