2016 CHEVROLET IMPALA Vehicle Speed Control Problems

WHEN YOU START IT THE SPEED AND RPM' S START JUMPING THE COOLANT GADGET WAVES AT YOU THEN WHEN YOU PUT IT IN REVERSE OR DRIVE IT BUMPS WHEN YOU DRIVING YOU DON'T KNOW HOW FAST YOU GOING BECAUSE OF THE GADGET BOUNCING UP AND DOWN TO TOP IT OFF ITS JUMPING THE WHOLE TIME YOU DRIVING IT.

WHILE DRIVING MY VEHICLE, THE RPM GOES TO 4 OR 5 WHILE ONLY ATTEMPTING TO DO SPEED LIMING, IT STALLS AND JERKS AS IF SOMEONE IS PULLING ON THE VEHICLE AS I TRY TO ACCELERATE. ON THE EXPRESSWAY, MY VEHICLE STRUGGLES TO HIT 40MPH - 60MPH WITHOUT IT FEELING FORCED AND RPM AT 5. IT STALLS TO REVERSE SOMETIMES AND STALLS TO TAKE OFF.

I DRIVE A 2015 CHEVY IMPALA, 3 DIFFERENT MECHANICS HAVE TOLD ME MY BRAKES ARE GOOD AS NEW AND I SHOULDN'T HAVE ANY PROBLEMS WITH THEM HOWEVER MY CAR IS STILL HAVING TROUBLE COMING TO A COMPLETE STOP AND IT'S SCARY BECAUSE NOT ONLY DO I HAVE TWO CHILDRE BUT I ALSO LIVE IN A SNOWY STATE.

I WAS STOPPED AT THE TOP OF THE HILL ON A PRIVATE ROAD. WHEN I TOOK MY FOOT OFF THE BRAKE AND PRESSED THE ACCELERATOR, NOTHING HAPPENED. THE CAR BEGAN TO ROLL BACKWARDS AND I PRESSED DOWN ON THE BRAKE. THE BRAKE WAS VERY WEAK AND IT TOOK 50-60 FEET AND ALL OF MY PRESSURE ON THE BRAKE PEDAL TO BRING THE CAR TO A STOP. AFTER I STOPPED, I REALIZED THAT THE ENGINE HAD TURNED OFF AND THE IGNITION WAS INT HE OFF POSITION. I ROTATED THE KEY IN THE IGNITION BACK TO THE START POSITION TO START THE ENGINE. I CONTINUED BACK UP THE HILL NORMALLY AFTER THE ENGINE WAS STARTED. LUCKILY, THERE WERE NO CARS BEHIND ME ON THE HILL OR THEY WOULD'VE BEEN HIT.