paying new prices on second new vehicles

I purchased a brand new 2018 H100 from hyundai Pinetown ,at 5000 km i started have a power ,brakes and gears issues . The van has a problem with power when carrying a load lighter than the 1,3tons , the gearbox had a winding sound ,then later became hard as ever like its a old truck . I have had the exhaust break off twice from the van , as it knocks against the chassis. Keep in mind the van has not done more than 35000km. I went through the manual of the car n it says if there is a problem at 10000km - 20000km it must be changed but it was not done . i had taken the full maintainance plan for the vehicle. yet the sales man that sold me the car says otherwise when i was purchasing it . The dealer Principle Mark refuses to talk to me concerning the vehicle, i called him several times and he doesn't respond to my calls even messages.