Hoi Kevin indeed its like your diagram shows. As i can see i use a mix of a daisy chain network and a star network. Is that a problem? Main deco ---> switch ----> deco first floor ----> And from Deco first floor ethernet cable to Deco second floor. And from the Deco on the second floor i have a switch connected that connects the ps4 and other. I could remove the switch after the main deco and hardwire it directly to the deco first floor to create a true daisy chain network, shall i try that? I have connected the ps4 directly to Deco on the second floor but it stil connects to the Deco one floor below. Its difficult for me to relocate the current Deco on the first floor do to the available ethernet wires

ok i dont get it anymore.

I removed all the switches and connected it as a daisy chain. 

Bottom floor works well Deco p7 as main deco and a M5 in the livingroom (connected through Wifi) Speeds are stable high and and stable. Only thing that is strange is that sometimes when i am furtest away from the main P7 deco and closest by the M5 it still connects my phone to the P7. Also i have a Thermostat that is almost on top of the M5 , but it still connects to the P7 that is far away. (maybe because the Thermostat can only use 2,4ghz???)

I siwtched the Deco P7 on the first floor with the one on the second floor. That seemed to solve (most of) the issue with not connecting to the nearest Deco. But still Deco on the first floor seems to be the one that is fastest in speed.

The Deo P7 on the second floor has massive dropouts in speed. When i do a speed check on the PS4 for instance, every time i check i get a very different result. one time its 190Mbps down and a few seconds later is drops to 80Mbps. Then the next test drops to 60Mbps. After it can go up to 110Mbps. 

It doesnt matter if i have the second floor Deco connected by Ethernet to the one on the first floor or that its connected by Wifi.

With ethernet it sometimes seems as it is internally in the Deco capped to 100Mbs or something becaus in the speedtest with a laptop wired to the Deco it cant go above the 100Mbps. 

On wifi I also tried with a laptop and speedtest.net. It goes up to 190Mbps but then drops back to 70Mbps.

Next step i think is to remove al Decos and set up everything from scratch.

i am thinking to maybe switch the Deco P7 on the second floor with the M5 in the living room. Dont know why but maybe it wil help.

@Kevin_Z

So i did some testing and switching of the Deco's in my house.

Situation now is:(daisy chain)

Bottom floor: Internet -> main Deco P7-> 1st floor Deco P7 wired and to a Deco P7 wireless in the livingroom on de bottom floor

First floor Deco P7 -> Deco M5 on the second floor wireless connection.

Here comes the strange part...If i connect the Deco P7 on the first floor to the M5 on the second floor via ethernet cable, connection is very unstable (says 1gbs tested on laptop but almost never exceeds 100mbps) Also if ik connect through wifi connection is also poor..(sometimes 140mbps and a bit later down tot 30mbps) 

Dont ask why but i connected a faulty ethernet cable and with that connected my speeds through wifi exceed even 200mbps. It sometimes drops back to 140 or something but much better than before.

So i dont get it.

connection tested on the Deco on the first floor are awesome (max 250mbps that is availlable) but connected from that Deco to the one on the second floor is faulty.

It should be ok right. If i have max speed on the first floor Deco and ik connect that one to the second floor deco bij ethernet cable. Ik should get the seem speed right???