2008 Nissan Altima coupe engine running hot if I turn heat up the coolant gage goes down when driving
Yep, because your heater acts as another radiator.
You need to find out why you have an overheating problem before serious engine damage occurs.
What you are doing with the heater settings might not work the next time.
How’s the coolant level in the overflow and the radiator (checked when the engine is cold of course)? Are the radiator fans coming on?
This was posted in “ask someone”, chances are the OP will not respond.