"He is a German painter."
Translation:Anh ấy là hoạ sĩ người Đức.
Can họa sĩ be used for both a painter like Van Gogh and also a painter who paints the side of a house?
Only for the former. "họa sỹ" refers to someone who paints as an art form. The act of painting a wall or painting houses is "sơn tường/nhà."
Not in this case. "Người" is used to indicate one person from a particular country. In the case of its absence, it usually is used to talk generally about many people from a particular country.
For example: 1. Ca sỹ người Nhật đó rất dễ thương. (That particular Japanese singer is very cute.) 2. Ca sỹ Nhật rất dễ thương (Japanese singers in general are very cute.)
Also, Đức (and Nhật) is a popular male name here in Vietnam, so it could be misunderstood as you are referring to an artist called "Đức."
I hope that wasn't too convoluted
On the contrary, it makes things clear. Thank you. I guess you can overcome both problems you mention by adding một, but I have learned that in that case you also have to add the classifier. So the người has to be added in any case.