My screen is glitching after I let it replaced to a local repairman

My phone slip on my phone while I am working with something. Then it faced down . I picked it up then it is white screened. The LCD was broken . I immediately bring it to the local repairman to let it fixed for a day then it came well. After a some weeks to a month , i noticed my phone glitching , sometimes flickering then overheating at the lower part of my phone. The repairman said that due to overheating and falling , my phone becomes like that and he told me to repair the screen again. I am skeptical at first because at the 1st day when I got my phone , it is overheating after 5-10 minutes of usage. What should I do?