Hi guys, need some advise. I have recently been turboed to 500Mbps.
My hardwares setup are :-
1) BTU - Alcatel Lucent I-240G-P (been with me since 2010 or 2011)
2) Wifi Router - TP Link Archer C7 V2
3) Cable from BTU to Wifi Router - Cat 5E

Problems:-
1) Tested WIFI speeds on Samsung Note 4, Ipad Air, Xiaomi Redmi Note 5 with Ookla on 5G band but could not achieve more than 180 Mbps download Wifi speeds. Have tried contacting TM but the technical department says due to recent upgrades, the speed are still not stable and ask me to be patient and will re-fresh my connections to see if there is any improvement which it did not. - Are my hardwares ready for 500 Mbps and are my WIFI testings accurate?

2) Bought a Cat 6 cable (brand - U Green) but when connected from BTU to Wfi Router, the WIFI connections becomes erratic, sometimes online, sometimes offline. I changed back to Cat 5E and it becomes stable. Is the Cat 6 cable not compatible or defective?
note - The Cat 6 cable was bought online and was quite cheap, maybe that's the problem.

Yes, it was bought from Ugreen flagship store in Lazada and it was the round one. Funny thing is that compared to the Cat 5E cable, the Cat6 cable looks thinner...lol.

It was on flash sale at that time and only cost RM4.08, I bought 2.

Yes, have tried to manually select the nearest server, still not getting more than 170 Mbps.

So, you think that my hardwares are ok to achieve 500 Mbps?

The Archer C7 V2, after I bought it and set it up last year, I did not do any firmware upgrades after that.
Do you think I need to do any firmware upgrades or other settings?

V2 is considered old. It is already V5 now.
No point setting to 80MHz, if your device does not support the MIMO required for the turbo speed.