Errors with permissions/connection

[kiwamijapan]

Yesterday I've installed qBittorrent webUI version on raspberry pi, but I have some strange problems. First of all, client show that torrents are stalled - I don't even know what does it mean (newbie here) and I can't find any solution for that. I've set uPnP service in my router, so ports are forwarded, but files still won't download. What's more, I wanted to change directory of the torrent and client says that 'Cannot write to the directory' - I suppose that's a problem with permissions. Where should I look for potential errors? Is it something with my router or configuration of the client on raspi? I'll provide .service file for qbittorrent and all other data about it if necessary.
Cheers