Today i tried again to find a solution. Looks like 2 apps on my notebook caused problems.
1) RivaTuner Statistics Server
2) Nvidia Geforce Experience Ingame Overlay (Display fps)
When i disabled the first one, i noticed a much smoother menu (opening animation), but combat still felt like 5 fps, even though the Nvidia Geforce Experience Overlay showed 30 fps in combat (with 60 fps battles enabled). Then i disabled the Geforce Overlay as well and now combat is as smooth as on my Desktop PC.
It looks like there was some kind of conflict with those apps. The funny thing is, that they are installed and running on my Desktop PC as well, but there i had no problems at all. I'm looking forward to the next update regardless. I really appreciate all the work the community has accomplished.