Before Gigaset - now Fritz scrap

Have been a Gigaset SX353 ISDNTelefon operated with 8 DECT extensions. Operating in my family house from the floor to the residential basement problem.
I then wanted to use the nice new functions of the Fritz-phone, especially a Fritz! Box 7390 is available.
Bought 4 Fritz phones MT-F.
Connection via FritzBox 7390 only on one floor and with an impossible voice quality.
So a Fritz DECT repeater acquired.
Now I had a part of the first floor and a part of the basement reception. The devices connected, however when changing the floors not to the stronger station.
So a Fritz Box 7490 bought (I had before anyway) and the 7390 set on the first floor as additional repeaters.
Now I had the whole house reception (my Gigaset managed the problems alone). Problem was, however, that the devices still only sporadically toggle the reverse video on the strong station.
I was standing next to a station and the device did not recognize this.
Added to this was a regular strong crack in the equipment and again abruptly disconnects.

Now I thought that competent AVM hotline could help me.
But I have not experienced.
If there are several (almost 10) various calls I've experienced from the denial of my problem until the sending of vacuous installation leaflets everything. Only no help for proper installation. The whole took several months because I totally agree AVM would be quality and the fault lies with me, have not returned to scrap (even in debt).

I am going to the 4 MT-F, the DECT repeater and the Fritz Box 7390 - sale in the bay - naturally at a loss.

The old Gigaset has now been reinstalled, good reception and voice quality class back.

Thank AVM - we are separated from today (except for the Fritz! Box). Never again even one for you.