If you do not need a full VPN, you can use a dynamic proxy via SSH to reach an internal computer from outside the Institute:

• Unix, MacOS-X: ssh -Dlocalhost:8888 username@login-stud.informatik.uni-bonn.de (students) or ssh -Dlocalhost:8888 username@login-staff.informatik.uni-bonn.de (employees) — replace “username” with your user name.
• Putty running on Windows:
  1. In Session: Host login-stud.informatik.uni-bonn.de (students) or login-staff.informatik.uni-bonn.de (employees)
  2. In Connection: open the sub-menu SSH
  3. In Tunnels: destination dynamic, source port 8888, ADD
  4. Then Open

Finally, configure in your web browser localhost:8888 as the Socks V5 proxy.

This example is for firefox 60.esr, English version. Other browsers and versions may look differently. Type, of course, 8888 wherever 7777 is used these pictures.