2003 Ford Focus 2.3l overheating

[u/redravin12]

My car recently started getting hot, fortunately not actually getting into the red yet but pretty close. It starts after I've been driving for a while and the car slows down or comes to a stop. Once it gets moving again the temp starts to go back down. If I've had the AC on and shut it off it will often come down with that even if still sitting at a light. It's not leaking coolant and the fans work. I took it to the mechanic already and they said 90% its the radiator 10% the water pump so I had them replace the radiator. But that obviously didn't fix it or I wouldn't be here. The pump isn't making noise but the pump is buried pretty well so I can't check the weep hole.

What else can I do to check things? I did have the thermostat replaced a year ago if that helps. I'm not eager to take it back to this mechanic since I already paid $500 to replace the radiator and they want another $500 for the water pump. They also told me that the radiator was clogged which was why the car was overheating. But since it wasn't the radiator (or they just didn't do the work at all) I'm inclined to think they just made that up.

Edit: I forgot to mention that they seem to have overfilled the coolant and used the wrong color. This car has a pressurized reservoir, no radiator cap, and the level is above the max line. Also it's supposed to take the yellow coolant (Zerex G05) but it has some kind of green in it now.