Top of iPhone heats up near the EMI shield

Hi, my iPhone is out of warranty and my wifi is greyed out, so I sent my phone for repair. The guy said that he needed 2 to 3 days to repair the wifi problem, but he couldn't fix it even after a week. So, after i got back my phone, i tried to remove the emi shield and see if there is something wrong. After i reassembled everything, My phone took really long to power on, and it only displays the red charging icon for around 1-2 hours. After it finally came on, it was charging at only 7%! I thought it would be fine already but when i let it charge and i opened Whatsapp, the phone immediately went down to 1% WHEN IT WAS CHARGING and then it died. Also, the phone was really hot too, the iPhone was displaying the heat warning message. I then decided to take out the emi shield and check if everything was in place and it was. I even cleaned the emi shield with a piece of tissue before closing my iPhone back. My iPhone never experienced water damage. I have tried a hard reset but it would not work too. And i'm sure that this isn't a battery problem, as the battery is not heated up at all but it is the top of the iPhone, near the emi shield and the Murata wifi chip that can literally fry an egg. Please help!