Usually with fibre it either works or doesn't. If your fibre connection is running bad on a cabled device then it could be a line fault. If you are testing on wifi, then you'd need to eliminate that as a cause first.
On your fibre connection a cabled speedtest should be 700Mbit+, often 900+. On wifi it can be anything from 30Mbit (2.4ghz wifi band) to 300-400Mbit (5ghz band) typically.