Look mate, I don't think it's a petrol thing, but give it a go as you're learning (me too).
You should do a full petrol flush...
E.g. run 1 full tank of, say, premium 91 octane petrol, then run it to the very last drop (or lost to it when the meter shows E) - then fill it up with something like Shell's VPower 100% Octane race fuel... then see if the difference is huge? IF that, then upgrade your fuel, if no difference then it must be something else.
In my ace, for some reason my car runs it's best only on Shell's Vpower and and BP's Ultimate petrol.
Good luck - also , you car might need a full service.