Port forwarding still not working?

Hello, I recently got a ZTE 5G outdoor router (MC889) outside my window, and a Deco X50 inside, to which I'm connected via Wi-Fi. My problem is that I'd like to open port 25565 on my PC for a Minecraft server , but it's not working properly. Port forwarding is only possible in the Deco app. There, I've selected port 25565 for my PC's IP address and selected TPC/UDP. However, the port is still not open, and I can't join the server.

Here are the most important settings I can make on the devices:

The ZTE outdoor router is in bridge mode and the Deco is in router mode by default, so I also opened the port on the Deco.

Why doesn't this work? Does anyone know what the problem is? :/
If any information is missing, please let me know.

thanks in advance