If you like give it an try but think of real tyre sizes.
These are different from manufacturer to manufacturer.
Semi-slicks tend to be wider than street tyres.
Jake/Danish-GTI has Toyo R1-R. You better ask him about
the real width an fitting on a Golf. Look at the manufacturer's
data as well. I guess most 235 semis are 240 - 244 mm wide.
Or just go for 225/40.