Slow wifi in Macbook Pro

Hi everybody,

I'm asking for help because the problem I'm having is driving me crazy.

I have a Macbook Pro connected via Wifi to a router which is right next to it. My connection goes up to 80mbps, which I can verify on the modem/router itself, on my iPhone which is itself connected to the same network, and my PC.

On my iPhone I have no problem, 80mbps. On my desktop PC no problem, still 80mbps. On my MBP (2016 with touchbar, with Mojave) when I restart the system it goes up to 60mbps, which is still not 80mbps but it's acceptable (but I still don't know why I can't reach 80mbps when at the same exact moment, on my iPhone, I get 80).

I have no problem for some hours, then I go away and just close the Macbook (not shutting it down or putting it to sleep, just closing the screen) and when I reopen it, boom, 10-20mbps is all I can get. The speedtest goes to 40/60mbps for half a second and then quickly goes down to 10-20. It stays at 10-20mbps until I restart the system, and when I restart, it goes up to 60 again.

This things is driving me CRAZY. The router has no specific configurations for my MBP (it's treated the same as my iPhone), I don't have any program using internet, I have tried deleting my wifi configuration files (it was explained in some article online) with no luck. Also, I have just upgraded to the latest version of Mojave, no luck either (I don't know if this thing happened with High Sierra because at the time I had a bad connection). Also my connection is working fine and always stays at 80mbps, which is the result I get running the speedtest on iPhone and PC.

Suggestions? Thank you!