Whenyou purchase the Oppo F11 pro, a few problems are also there with this phone due to the same reason. However, they can be fixed and you can do so easily by paying attention to this post. So, all you have to do is to make sure this post is followed correctly to eliminate the various problems you are facing.  Make sure the glass guard 
1 The counterfeit or third-party batteries and chargers might be improperly designed which would cause safety problems. Non-OPPO official Service Centers might not be able to provide professional repair tools or repair processes, professional training of technical support for OPPO products, so the batteries and other spare parts might be damaged during repair causing substandard performance.