Snaps run in a confined environment. You have to allow it access & permission to do what it wants.
I have no idea how though; frankly I see no reason why you'd even want to use a snap application for what you want to achieve.

why not just 'apt install something-that-works'.

Creating a bootable USB - usually the distro you want to install has instructions on how to do it.
If not, this is one of the most asked & answered topics around Linux - a few web searches should set you up with half a dozen options.

BTW, I notice that you are running your desktop as root? That is most likely wrong, and anyhow you don't need sudo if you do that.

Well, ondoho, i did not found 'something-that-works' and no instruction that works after a long time of try-and-error so i came here to find help.

We can close this thread, because i came to the conclusion: its not worth to put more effort in this, because the laptop is too old, so i bought a new one with alread windows installed : ) now i can play games \o/

That's fine, Linux isn't for everybody. Enjoy your new laptop/OS!