SOLVED: FortiClient with Unitymedia Connect Box: no internet via LAN

I had my laptop connected to Connect Box via Wifi, everything was fine. Then I got FortiClient for VPN connection to my companies network. VPN network was fine, internet connection at home as well. Now I connect my laptop to Connect Box via LAN. I have to active connections betwenn Connect Box and my laptop: WLAN 72 MBit/s and Ethernet 1000 MBit/s. But unfortunately: Ethernet has no internet, even if FortiClient is not running and active. I have to choose if I would like to have internet connection with slow connection to my private network (with NAS) or if I need fast file transfer in network, but do not have internet connection.

I have another laptop connected via ethernet (without FortiClient) which works fine. Both PCs are running Windows 10.

What do I have to change/check to get internet and fast network via ethernet?