I have looked at several other posts. Please be patient. I'm a 57 yo female who is NOT a mechanic but I can follow directions. (better with video)

So AC blows very cold at high speeds (highway, interstate etc) The slower the speed the warmer the air gets. I just realized that if the car is at idle, It starts to overheat. ONLY time it does this. AC on, idle.

Just started the car (not warmed up but it is 90 degrees in the south), turned on AC and checked the fans. (When facing the engine) the left fan is working. The right one is NOT moving.

What appears to be happening (I could be wrong but makes sense as a non mechanic) is that at high speeds the air is turning the fan but the slower I go the less air passing through. I am dying not using the AC in the summer in the south because I do a lot of in town driving. And having the windows down at slow speeds does nothing. But also concerned because someone told me this could lead to more issues. Any help would be great if you could just speak to me as a NON mechanic. TIA