@Hakim9999 

Hi, welcome to the community.

I think the wireless devices might be connected to 2.4ghz.

Could you please help me run the following test:

1. unplug any other satellite units if there is more than one.

2. turn off 2.4ghz on the Deco APP and leave the 5ghz only, then test the internet speed again.

3. Please also check the current link speed on the device:How to check the associated/link speed on a wireless client

Thank you.

Best regards.