Thnx TIG for trying to help me. Yesterday I installed sketchup the way you suggested, sitting on a couch using the touchpad. After doing so, I opened Sketchup to see whether the issue was solved and it seemed to be functioning the way it should, finally!
To be sure, I connected the mouse to the laptop and once again I was experiencing the delay issue with shortcuts. So it wasn't Sketchup nor the hardware which was causing the delay, but it turned out to be the mouse! Since it was functioning fine otherwise, I never even considered the mouse to be the problem. After reinstalling the mouse driver the problem was finally solved. It's so simple if you know where to look.... )
So PROBLEM SOLVED! Thnx for helping!