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What‘s the problem?

Looks as if Oil is burned. Well, it happens when there‘s a problem with some gaskets.
From experience I can tell you, that chances are, the driver doesn‘t know about his blue smoke.
He will notice soon that there is some oil missing.

Could also have other issues, but when there is water/coolant burned, there‘s rather a whole lot of white smoke.

Edit:
Chances are that this vehicle is registered as a Camionette, category N1 and with that, he needs to see TÜV once per year.
When they check the exhaust gasses at SNCT, they will pull him out.