AX600 (RBR850/RBS850) - Wifi dropping

Hi,

I just boght the AX6000 (RBR850/RBS850). My ISP's (Bell) combo router / modem works in bridge mode. 1 Gbps (download / upload).

House: 3 levels.

• Basement: ISP Router / Modem and Orbi Router (RBR850)
• 1 Level: Nothing installed.
• 2 Level: Orbi satellite (RBS850). This one is connected via an Ethernet cable to the Orbi Router.

So, Ethernet connection on the Orbi router and Orbi satellite are fine. I receive the maximum speed. 

Problems:

• Wi-fi is dropping all the time on the cellphones 
• Wi-fi coverage is not good 
  • Bedroom speed (5 meters): 50-150 Mbps
  • Close to the orbi satellite on wifi: 
    • Macbook pro : 400-550 Mbps (connected on 5G)
    • Huawei P20 pro: 350 Mbps - 400Mbps (connected on 5G) 

I already tried/read multiple solutions in the forum with no successful results. Wifi keeps jumping all the time. 

Thanks for any ideas or solution.