Improve, fix and clarify Surface docs

[damusss]

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Some parts of the docs had smaller errors. Some parts were basically lying. Big methods and the constructor where very convoluted throwing information randomly. I didn't change everything, but rephrased things. Also, in the constructor and in convert, I thought that the docs weren't even trying to explain how the arguments worked, so I looked at the actual code and refined them. I'm open for suggestions of course.