Thanks! 
I used 4.11 preview with light portals in every window. A skylight with low intensity (2) and a directional light with low intensity (1). I increased the brightness a little in PostProcessVolume. After that I added spotlights on the ceilings with intensity of 60-80 to fill up rooms that are to dark I tweaked the baselightmass.ini to use 512 NumHemisPhereSamples and baked on Medium Settings The bake took a good night or so. After that I tweaked the PostProcess again with Vignette and a LUT