Mulfunction after service

hi there. i took my Fiesta to FORD FURY WILLIAM NICOL around May 2018 to fix my petrol gauge not reading properly. so when i fill up full tank it gives me 365km distance before it was reading 620km estimated distance. i took my car there about 5 times no luck. the reason i am complaining is because my car is auto so whatever they were fiddling my car is now shaking when i apply brakes on a bump to bump motion...i have been battling since then hoping it will come alright. two problems: petrol gauge not reading properly and car shakes like it lost timing.