Welcome to JA.
Sounds like you may still have some air in the system. Here is how to bleed it. Remove the bleeder screw on the upper radiator hose. Remove the coolant tank cap. Locate the tank overflow tube coming out of the coolant cap neck. Rotate it up so the end of it is sticking up. Make sure the coolant is full. Put your hand over the cap hole on the tank to seal it. The blow in the overflow tube until coolant comes out of the bleeder without any air. Make sure the coolant level does not go down low or it will push in more air. Try this first. These things can be hard to get the air out sometimes. If you are unsucessful with that then you can reverse the heater hoses and that will get the air of the heater core because that is usually where the air is in the system.
I would then check the radiator for blockages. You will need to get an infared thermometer. Get the car up to temp and then check the temp starting at the bottom of the radiator from bottom to top and across it. If you find any excessively hot spots compared to the rest of the radiator then it has a blockage it. It should get cooler progressively cooler from bottom to top.