How do I get WiFi and phone service, technology in the basement

The mesh with Fritz Router (in the attic) and Fritz Repeater (connected as access point on the ground floor via LAN) runs smoothly for me. Calling over WLAN with handover works without problems. I rather have the problem of getting the DECT signal from the attic through the upper floor into the ground floor. The DECT repeater does not work as desired yet ...

For me, the mesh with Fritz Router (in the attic) and Fritz Repeater (connected as an access point on the ground floor via LAN) runs smoothly. Calling over WLAN with handover works without any problems.

I rather have the problem of getting the DECT signal from the attic through the upper floor to the ground floor. The DECT repeater doesn't work as desired yet ...

That should be easily solvable with two IP-DECT stations, right?

This should be easily solvable with two IP-DECT stations, right?

Do you have a suggestion?

This is absolutely not nonsense. Just tell that to devices with poor WLAN chips like a Fire Tablet or every second mid-range phone. They do endpoint-hopping endlessly because the signal from one access point does not always reach the device well, and the device then switches.

First of all, I do not assume any faulty devices (my Fire Tablet is also completely unremarkable in this regard), on the other hand, there are other solutions for such problems, but basically the device SHOULD switch when reception is poor. To enable this control, there are corresponding management solutions, but in a single-family house, I still consider the solution with one SSID to be the best option if you do not want to switch manually all the time.

In my example, it was about when the FB also broadcasts Wi-Fi. In that case, it makes sense to set up the FB repeaters as access points, because FB and access points then broadcast the same SSID and negotiate among themselves which connection point is best for the client. If you want the FB to broadcast Wi-Fi and use the Unifi as an access point, you either have to use different SSIDs or give both the same SSID, which will inevitably cause problems for clients because they don't know which one of the two they should connect to best.

I don't quite understand why it is better to turn off the Wi-Fi of the Fritzbox?
I have the FritzBox in the basement, and on the ground floor and attic respectively, a Unifi Accesspoint AC-Pro.
All devices always connect to the access point/Fritzbox depending on where you are in the house.
All broadcast on the same SSID.

When I am in the basement, my phone connects to the Fritzbox; when I go upstairs and enter the living room, my phone switches to the access point on the ground floor.

First of all, I do not assume any faulty end devices (my Fire Tablet is completely unremarkable in this respect)

It is not about faulty end devices but about completely normal devices as they are sold as standard today. Of course your Fire Tablet is unremarkable if you do not deal with the topic. If you currently let two different endpoints broadcast the same SSID, change one SSID and be surprised how much longer the battery of your Fire Tablet lasts. You will notice this immediately within three days.

but basically the device SHOULD switch in case of poor reception.

Of course it should be like that, but if this happens every three minutes due to signal strength that does NOT come from the access point but from the end device, it is counterproductive.

There are corresponding management solutions to enable this control, but in a single-family house I still consider the solution with one SSID to be the best if you don't want to switch manually all the time.

We agree on that. That is why I said that if a FritzBox is used, ideally also a FritzRepeater is used as an access point, because then the FB access point and the client determine to which one the client connects. But that has nothing to do with mesh Wi-Fi.

I don't quite understand why it is better to turn off the Wi-Fi of the FritzBox?

To avoid hopping between the networks. If that is not the case for you, for example because your basement ceiling dampens the basement Wi-Fi strongly enough, then it is not better to turn off the Wi-Fi of the FB but irrelevant.