Depending on your settings & downloading behavior, you are sharing either no files or just the files you've downloaded from the BitTorrent network.
Here are the possibilities:
If you download something from the BitTorrent network and you choose to seed your downloads in your Preferences, then you are sharing only those files with your fellow downloaders and you will see them as active & seeding in the Transfers section. Once you clear them from Transfers, they are not seeding = not being shared anymore.
If you don't choose to seed your BitTorrent downloads, then you will not be sharing any files by default, but know that it's a norm that you should seed your downloads at least one to one [send as much data as you received. The more you seed the faster the downloads will be for others. The more others seed, the faster will the downloads be for you!]
My Files section is only a simplified file explorer. FrostWire scans your phone (or folders choose on FrostWire desktop) and shows you the media files you have for easier access. That doesn't mean you are sharing these files. Your files are available only for you, visible only by you and no one else will access them.