@Annick007 

Good day.

Did you mean the wireless speed about M5 is horrible.

 If yes, could you please refer to the following suggestion:

1. How much speed you could get from the modem?---it would be much better to test the modem with a laptop directly connected by cable?
2. What is the speed test via Deco APP? And could you please also run a speed test on the computer when it is connected via cable to the main Deco?
3. How about the wireless speed from the main Deco,  and also from the satellite Deco?
4. How are the Decos connected to each other, wirelessly or Ethernet connection?

After that, please turn off the QoS, antivirus as well as the parental control on the Deco APP;

Thank you very much.