Thank you both for listening and commenting.
I turned the guitar tracks a little lower, thus bringing vocals, drums, and bass a bit more upfront in the mix. That's as much as I as a layman 'producer' seem to be able to achieve. Thanks a lot for pointing that out.
As for my timing, a lot of my problems there are due to the different latency effects that Cubase produces - in addition to my amateurish performance. I edit them as good I can, but I can't say that I like it...
Bernd
* different for audio and Midi, and also different depending on the VST you use - quite a mess