I have found the solution to my own problem. It turned out that Windows applied firewall rules to the traffic of the server. I thought that I had permanently turned off my firewall years ago,but I only turned it of for private connexions. Windows considered the network adapter of the server a public connexion. I changed it to private, so the firewall rules did not apply. Here is how I did that:
https://www.howto-connect.com/change-public-vpn-private-windows-10/
It also turned out that the client ignores pushed routes, so I added the route to the home subnet in the client config.
Thanks to those who payed attention.
