Malware attacks phone heating

Although I'm personally skeptical that your phone overheating is caused by malware, I can't definitively say it's not, so we'll work with what you've stated.

First step is to get rid of the malware. Back up all your data and restore your phone to factory settings. Once the entire system has been reloaded, the malware won't be able to re-infect your phone unless you help it, either by downloading an infected app or visiting a website that installs the malware on your phone, so if you avoid both of those scenarios you should be good. When you go to restore your data, be sure to not reinstall your apps yet. Go through the ones you want and make sure you download them from reputable sites like the Google Play Store.

If that doesn't fix the problem, you could always go with what would have been my first suggestion, to replace the battery.

Manuales / LG Q6 / Battery - Nadie Me Llama Gallina