take the radiator out and flush it really good,
put a hose in the pipe with something wrapped around it to create a seal and blast the insides out, rotate the radiator on the edge flushing on the side uspide down etc.
Then repeat for the other hole. Leave the radiator cap on.
Also take out your thermometer and put it in a cup of hot water and make sure its opening.
While the radiator is out, reverse flush your engine, same as like the radiator, flush through the top hose then the lower hose.
Make sure when you refill the radiator the car is flat or nose up to prevent air leaks.
Try all that if its still running hot prob time to reco the one you have, or find a good 2nd hand one.
EDIT: If it hasnt had it done recently you may as well do the oil / filter while you are at it.
Good luck.
Reed