To be honest, I don't understand it at all, so I'm looking for the help of specialists who will help me solve this and other issues.

I don't recommend using free domains because it is better to pay and get good service and quality services than to suffer with a free domain that can cause problems. As for specialists, I can advise https://www.namecheap.com/domains/. In my opinion, this is a great company that will take care of the registration and management of the domain.