I have freshly installed KSP via steam and tried to reinstall it a few times but with no effect. After launching KSP a black window with a cursor pops up. It appears as KSP is starting up corectly. After a while the start menu song starts playing. there is just no graphics. The log confirms my claim.
Log:
https://pastebin.com/4sGjkYnr
sorry for my bad english...