Are these fixed phrases?

No, I think they can be translated literally, if you are circumspect about it.

I think you can take them word by word.

And what about: keep (it) cool, open (it) wide, paint (it) red - I think there are more posibilities here, aren't they?

You are not speaking of fixed phrases, Aleka; you are speaking of idioms. There is no way that we can judge for you whether 'paint it red' is used in a literal sense or in an idiomatic sense unless we see it in context.

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It is just a list in a textbook - "A few verbs that combine with an object + adjectival complement." So I don't understand if it is only an example of a large number of verbs which can be used this way, or if it is a complete list. I've thought, that it is the former, and f.e. paint (it) red means, that something was white, I took a brush and made it red. I've tried to find them in a dicti

It says 'a few verbs', which means, and I agree, that there are a large number of verbs which can be used that way-- probably too many to list. Most of these phrases you will not find in the dictionary. However, when they have an idiomatic meaning, like paint (something) red, you should be able to find it [url=