Worst WiFi ever

I hate this stupid company , I have had my fire for a yr now I had absolutely no problems. The last 2 months the WiFi has just had a poor connection. A technician came out he rather says we must get an extender. The 4g does not connect at all. And not all devices connect to 5g. I'm paying 1000 for what fiber that's not working I'm really annoyed. It's either the router or the fibre line how can a 100mb line push out less than 10mbps and the 4g doesn't connect. Fix my damn problem. Quick to take ur money for a *** service.