heats up and wont cool down

I would guess the electric fan cannot move enough air and there is an air flow issue thru the radiator at speed. Do you have an "air dam" under your radiator core support or on your front bumper to direct air thru the grille and the radiator instead of allowing it to flow under the car? At speeds above 15 - 20 mph, you are probably building pressure under your engine bay stalling air flow thu the radiator. Your radiator air flow then solely relies on your electric fan to force air thru the radiator and that is probably insufficient. I have had excellent improvements in cooling at driving speeds by adding an air dam under the radiator core support on many vehicles. You also probably need a factory thermostatic clutch fan with a factory fan shroud instead of an electric fan since a factory clutch fan will move 6000-8000 cfm.