Port sharing without router access?

I want to make a minecraft server.

I want it to be public that everyone can join.

Then you need access to the settings interface of your router, or you host externally, for example at mine-hoster.de

Have no money

How do I get into the settings

I don't know which router you have. Just google "router name settings"

Using mc4u.de is free

Then it's best to use Aternos or Hamachi