How to say in Czech: Where did they learn Vietnamese?

English
Where did learn
Czech
Kde se naučili vietnamsky?
Are they learning Vietnamese?
Are they learning Vietnamese on their own?
They are learning Vietnamese.
Do they speak Vietnamese?
They do not speak Vietnamese.
They do not speak Vietnamese very well.
They speak only a little Vietnamese.
They speak Vietnamese.
They speak Vietnamese fluently.
They speak Vietnamese very well.

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