Internet problems how can I fix them?

I have internet problems for several weeks.

ie i will eg. With Fortnite logged off after 1 to 2 rounds. The problem is not only in Fortnite it also occurs in any other games. My internet is very slow although we actually have a good router and a good line. To solve the problem I have to either run the Winternet Troubleshooter several times or reboot my computer. All drivers are up to date and I use a repeater that is connected to the router from and then connected to me via Lan cable [I do not know if that is so optimal].

Best call your provider and ca in 78 hours or earlier that is usually fixed. If it is still like this you should get 1&1

Would it really recommend