Poor WiFi in the new building despite fiber optics

Did you perform a reset of the Fritzbox before the new setup in the house?

Your LAN is not disabled, you can see that in the first screenshot you took where LAN 1 is active.

The reason your laptop is not using the LAN could be that it prefers to log in via WLAN and therefore does not use LAN.

You don't need to change anything about the wiring.

When you have the access point running later, you will have full download speed.

The corner of the installation still needs to be prepared.

I assume the blue ones are the network cables? Are there really a staggering 4 simplex cables for the whole house? Wow... I've never seen fewer, 7x simplex was the previous lowest record (or nothing in old houses). But well, everything goes over WLAN anyway ;)

Jokes aside, if there really are only 4 cables, terminate them on 2 duplex sockets (as a patch panel substitute) in the utility room. Connect these to the router (yellow ports). Then put the AVM 2400 upstairs (first floor) into a power outlet. Set it up as a WLAN bridge, connect a patch cable from the AVM 2400 to the LAN socket upstairs. Done.

When I read all this, I really think a service should be offered for [Häuslebauer] and [Elis]. WLAN simulation on building plans. Once through the model house park and reference measurements made for the attenuations. Ekahau on, let's go...

If I read all this, I really think a service should be offered for homebuilders and Elis. WLAN simulation on building plans. One trip through the model house park and reference measurements made for the attenuations. Ekahau on, let's go...

Totally crazy idea :) There are supposed to be companies that offer exactly that... but unfortunately not many people are interested because 99.99999% of homebuilders go about it exactly like the thread creator here. The Fritzbox will work fine and you don't need cables anyway, there's WLAN. I could go on about that for days.

But as a special offer for electricians or interested home builders... I never looked for that. We do that too, but not for 160 sqm, rather for 160,000....