Thanks for your answer.
My Raspi is connected via HDMI to my TV. But I've got a second TV and the mobile items too. So it is a idea to use Libreelec like a server for all of them. And UPnP is one option to connect it. But I will test SMB or NFS as well.
Please describe your last thing for me. What will I have to change with my video database? And where? Do you have an example for me?