Overheating

I bought the car May 1, 2019. test drove it in the city and on the highway with my best friend and it drove great no overheating no other known issues. About a month later it started overheating. The check engine light came on and the code was for the thermostat. I had that replaced and noticed the radiator cap had been melted and that the reservoir cap was missing so I replaced those caps the same day as the thermostat. It drove fine for about a week and a half then it overheated again and the radiator cap melted again. This time the code was for the temp sensor. So I had that and the radiator cap replaced again. About a week later it overheated again and the only code was for a cylinder 2 misfire (there were no obvious signs of this but i went ahead and ordered new spark plugs and coils). The reservoir cap was missing and once again the radiator cap was melted. So I got a new radiator put in and another radiator cap the car drove fine for about 4 days and it overheated again. No codes this time aside from the cylinder 2 misfire (still waiting on parts to arrive). There was no obvious signs that its the water pump or the engine heads but I was told either or both of those things could be the issue as to why its still overheating. I just need some help with what to do next.