IPsec with Windows 10 VPN-Client slow

[Stephan84]

Hi,
I have now installed an IPSec server with the Opensense in addition to an OpenVPN server and would like to operate it with the WIndows 10 VPN client. I have included the instructions

  https://administrator.de/wissen/ipsec-vpn-mobile-benutzer-pfsense-opnsense-firewall-einrichten-337198.html

held and everything works! But the tunnel is very slow, if I use the OpenVPN tunnel via LTE on the computer, I get an upload of 15 MBit / s, if I use the IPSec tunnel it is only 5 MBit / s. The crazy thing is yet to come! If I use NCP instead of IKEv2 MSCHAPv2 IKEv1 I get the same speed as with the OpenVPN tunnel. It has something to do with the Windwos 10 VPN client in connection with IKEv2 and MSCHAPv2.
Really strange...
Has anyone implemented a fast working IPSec configuration with the WIndows VPN client?

I'm grateful for any help!

many Greetings
Stephan