Then what you need is a VPN that supports port forwarding. There are very few, but I bet you can find a thread somewhere on Lemmy discussing the options you have. Then, if I’m not mistaken, you still need to know/set the port number in your torrent client and config the router correctly, probably through its admin site which you’ll find on the router’s IP in the browser. If you don’t know the login (and admin/admin doesn’t work) you can find the default credentials by searching the web for your router model number + admin login. When logged in, you can set new admin login credentials if you don’t want other users of your local network to be able to access or change the config settings.

Check the open port number of your torrent client – which should also be set in your router’s port forwarding or firewall config (alternatively enable UPnP in the router config to let it handle such things for you).

You can use a utility like CanYouSeeMe.org to check if it’s correctly configured.

EDIT If you can’t make it work, you might be behind double NAT, sharing varying IPs with multiple other of the ISP’s customers at once. In that case, you’ll need to find one of the few trustworthy VPN providers that support port forwarding to get connectable, as it’s called, and be able to connect to all peers no matter if they’re connectable or not. Alternatively, rent a connectable seedbox in the cloud.

Set a different download directory for those, or put a label on them. That’ll make it easier to untangle and efficiently delete all those you don’t want to keep.