Many thx for that URL. At least on a another PC, i could now import the Cert as a machine certificate and much more important, the connection was now successfully! That's so great! I have 2 new problems now. First, for testing, i used "rightdns=8.8.8.8,8.8.4.4" to send the client the DNS server information and with "rightsourceip=%dhcp" i get an IP-address from my DHCP server. Now i have changed rightdns to a local DNS server, reconnected and i have still the old ones from Google as DNS. However the IP-address was changed to a new one. Why does the DNS not changed and how can i do this? If i start the server again with the new config, i can see, that only the new, local DNS is in the config. But it isn't in effect at the Windows 10 client.
The second problem is, that i have a connection to the VPN, but for internet access the Wifi connection is used. There should be a option, where i should set the VPN to the one and only connection which s available for internet traffic. But im sure, i can find at least this myself. But the above DNS thing makes nervous. If the DNS thing is solved, i try to connect my Android phone.