That can be everything, knowing all you told. So there many possible solutions. Although it's possible there is no solution at all either.

1. Your PC. Try another one or a laptop.
2. Your WiFi. Try an Ethernet-cable instead.
3. The connection with your ISP, starting with the modem. Contact your ISP.
4. The server at the university. Try Dropbox or so and sent a link to your teacher if it turns out that you can read them yourself without any errors.
5. Send them during the night when everything is quiet.