My bike shifting won’t surpass 6 I own a Scott Aspect 740. On the shifter it says it is on gear 7, 8 or 9 however in reality on the rear derailleur the chain is only on 6 and won’t go past this.

I’m looking for a fix as it is very annoying having to change into say a 3 and a 4 rather than my preferred 2 and an 8 for downhill riding.
It sounds like your derailleur cable has a bit of slack in it. You will find this video useful, its easier to give you this link with a lot of good footage than try to explain it myself.