Acceleration, Steering wheel and brake system problem

When trying to merge onto a freeway, my 2008 GMC Acadia barely step up to the game even after pressing down very hard on the gas. I am unable to speed up after completely stopping at a traffic light. It literally takes me a good 1-2 minutes before going from a speed of zero to 45 mph. People are always trying to cut me as they merging and then they look at me like I don't know how to drive on the freeway. Then there is good old steering wheel problem. It shakes really bad when I'm trying to slow down, even from speeds of 25 -30 mph and shakes my hand when braking to slow down on a freeway. And then the brake system problem is another one. When trying to brake and slow down, the steering wheel is not the only problem, the car makes a jerking movement as well. Just the other day, my mother asked if I was pushing the brakes again and again when trying to stop, but in reality I was pressing the brakes slightly to slow down enough to stop for the traffic light. I hate GMC's. I also had the daylight fixed as soon as I bought car in 2011 at 32,000 miles and it still continues to burn out from time to time. I turned the automatic lights off as I enter the car during daytime now. GMC manufacturer's, please stop making all these extra features if you are unable to fix it later for good. I have been taking it the car dealer services every few months and that's not just to get my oil change. What can I do to fix the 3 problems as described? HELP!