Wi-Fi is super slow

[Wroetoberg]

I've recently switched to BT and got the 150 MBPS plan with full fibre optic. The problem is that I constantly get up to or less than 30Mbps and it is very unstable. Another major problem is that my laptop which has a Wi-Fi 6 chip can only run Wi-Fi 4 for some reason and I am therefore getting speeds in kbs. I also use a Linksys WiFi extender but that has since stopped working and doesn't allow me to connect. Not sure if I set it up wrong or do I have to call a technican in to help. 

[spile]

To make the most of your broadband speed use wired network connections when possible. 

[Wroetoberg]

Hi, I get that ethernet has to be quicker but that still doesn't explain why my laptop decides to run WiFi 4 when on my hotspot it is running WiFi 6. Unfortunately I don't have a ethernet port or a ethernet cable that's long enough anyway.