@smokpl This shows how many you can be downloading simultaneously: https://www.gaytorrent.ru/rules.php?lan=1#96
Ratio for sharing needs to be at least a full 1:00 (1 to 1) to be fair, but to share more than that will be great for your ratio and helps build up a buffer in case you need it for a torrent that you want.
No limit on how many finished torrents you can keep seeding (after hopefully reaching the fair 1:1), other than your personal goals or equipment/bandwidth limits.