The template is mainly providing the materials so lighting is not really part of it. I am not a lighting artist - I am actually always struggling with this and my understanding is that indoor lighting is even more complicated. I remember reading somewhere about an option to tick to help cycles to understand where the light is coming from (e.g. a plane behind a window with special options).

Anyway, if someone has some good information I would take it too.

See https://www.blenderguru.com/?s=lighting

Gaffer by Greg Zaal seems to be a good and affordable addon for lighting (besides Andrew's Pro-Lighting Studio, even though not really cheap). I think I'll give it a try in the next days. HDRI lighting with always the same map is somewhat boring...

@Srubs: did you mean Portals?

Yes, this is it!
I agree with you HDR environment with the same few files is quite boring after a few renders.
Just looked at Gaffer. It seems to be interesting.