So apologies for the delay. Friend came around and fiddled with the settings as described in the first link, and while it seems kept the temperatures stable, the crashes still remained (although less frequent). The error message is still the same. (the moments it crashed werent during intensive games either...)
As mentioned, I did contact the reseller before and as I'm not in the position to dismantle the pc, send the cpu back and wait 3-4 weeks (or longer with the holidays). I therefore went fill nuclear and decided to buy a new prebuild/assembled pc from another retailer(with black friday promo), and scrap the current ones for parts to sell them on.
Ive kinda made my peace with it that I will make a loss now, but the peace of mind that now a company is responsible and if anything would be wrong I can go to them makes it a better option.
Already I can sell the GFX card to a friend, and when I dismantle the pc and send the cpu back, with a bit of luck I will have a brand new one to resell.
Thank you for your efforts though