Hi, welcome to the forums!
Don’t feel troubled: we’re all hosting from home, and run into the same or similar problems!
You mentioning ‘Fritz box’ triggered me thinking it is not a port issue per se. Did you try connecting from outside your LAN, eg, via mobile phone to your nohost.me domain?
Fritz boxes come with a ‘DNS rebind protection’ feature. It prevents websites from pointing to an IP in your LAN, because mostly they don’t have anything to do there.
You can look in the AVM documentation for details; in short, you have to enter your domain here (where it says online.osba.nl in my case):
When you are sick of entering portforwardings via the Fritz-GUI, have a look at editing the configuration as text. After changing anything, you need to generate a checksum for the FB to accept the configuration, the program you need is fritzchecksum (Python). Be sure to have a un-edited backup as well, in case you mess things up (else you have to reset your FB and start all over).