How to say in Czech: Is he learning Japanese on his own?

English
Is learning on his own?
Czech
On se učí japonsky jako samouk?
He is learning Japanese.
Is he learning Japanese?
Where did he learn Japanese?
His Japanese is getting better.
His Japanese is very good.
His native language is Japanese.
How good is his Japanese?
He is Japanese.
He is not Japanese.
Is he Japanese?

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