How to say in Czech: Do they speak Vietnamese?

English
Do speak
Czech
Mluví vietnamsky?
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.
Does anybody here speak Vietnamese?
Where did they learn Vietnamese?
Are they learning Vietnamese?
Are they learning Vietnamese on their own?

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