So after having some looks at bitcoin mining and setting up nicehash on my pc (single gtx 970) to have a look at how it works (ofcourse I won't be able to make any profit because of power consumption), I wondered if buying an Antminer S9 and starting to mine at home with a powercost of 0,26$/KwH would be profitable or will I just lose my investment.
As long as your mining device can pay for the electricity cost and have a little profit then you can continue mining. Think of it as getting a bitcoin from nowhere. even if you are just getting a little fraction of the coin every month if the price goes high after several years you can compute your earning by that time.