Jazakallah Khair brother for encouraging! InshaAllah you'll get much much better mileage as time goes and as you learn more.
I was asked by many people about how 'difficult' it was for them to drive slow, and I say to them why don't we just enjoy and relax and calm down a little bit so that we save money plus enjoy the drive
You should be able to get 20 KPL easily by maintaining your speed at 90 Km/h. Best of Luck. Jazakallah Khair once again brother!