My car continue to overheat while running in idle or at low speeds

I agree with Tom. Look at the fan operation, coolant level and thermostat first. You will probably find the problem with one of those and they are simple to fix. Water pump and head gasket are significantly harder to repair and should not be attempted by a novice.

And who did your coolant replacement? Air trapped in the system after being drained and refilled is extremely common and will cause overheating. If it was a shop, they probably knew to bleed the air out and its likely OK, but if it was a do it yourselfer project you might want to check again for air in the system. There is a bleeder valve near the thermostat.

Honestly I've fixed the fan relay cause that's what I thought happened. Fan started working, coolant is topped off and the thermostat is fine water pump is fine for whatever reason it always gets hot when I'm at idle for more than 3-5 minutes

I have a 2007 Pontiac Grand Prix GT. I had the same exact problem if I drove in 2nd gear while I was on the highway and kept the RPMs up it would not overheat. Bottom line, after playing with it for quite some time, checking out the coolant level, changing the thermostat, backflushing the heater core, it ended up being the water pump. When I took the water pump off the fan blade on the back of the water pump was completely disintegrated. It looks like a Chinese Star.