Thanks for the replies!
@growl_ey
I tried it with these settings and indeed, the reflections are better. The most impact has the “max refraction bounces” setting which was set to 0. Setting this to 4 like suggested gives a more clean reflection (not perfect yet), but the interior becomes all black now. There is no light passing through my windows now. Enabling skylight leaking brings back some light, but has a artificial look.
@comlys
Yes, it is hardware-raytraced and set up with hit lighting for reflections
