I got ya, same here, not all roses and cherries here in the States, depends where you live too. I got lucky that Snoop Dogg lives here in California, LOL. We're under the "Legal Medical Marijuana" umbrella. We can grow 6 plants per household and if you have a medical marijuana card I think that goes to 24 plants per household. And the laws have changed such that if you get caught growing more than the legal limit without a growers license..$500 ticket. lmfao..no wait, maybe we do have it good out here. So dam, that sucks, I don't see why they won't let you grow in your own house, kinda of misleading naming Spain like they do as a cannabis friendly country.
Organic soil is the worst for gnat control, they just thrive in that environment and media, if it's really to crazy and out of hand for you I'd look into growing in some good pure Coco Coir and just go synthetics. That would be my last attempt if it ever got to an apocalyptic invasion of these gnats. An oscillating fan at the pot level helps a lot too, your literally blowing those fuckers off and away from the top soil.
I grow for my friends and myself, (yes I'm popular)

and I pride myself in sharing the best flower I can give out. I had folks at the beginning that would tell me "keep trying, your not there yet" to my face. Didn't discourage me at all. just lit a fire inside to try harder. I've messed up a lot of grows, some on threads that lead to some embarrassing, sorry guys nothing to see here moments. Just got to keep going, the journey is just as important if not more, than the arrival. I grow because it's therapeutic for me. And a lot of fun.