How can I edit the config.php - to 'overwriteprotocol' => 'https'?

So I’ve found that I’ve got to edit the config.php file. But I don’t know how to do this.

So I’ve tried
nano /root/app/config/config.php - then I’ve get “permission” denied

When I try with sudo it says /root/app/config does not exist

If I try to access it via windows explorer it says that I need permission

As you can tell - I’m new to this and try to learn.

The installation is made with docker/portainer and it works fine except that I get a login-failure and have to refresh the login-page.

Hopefully someone can explain what I need to do.

Thanks in advance…