I know a lot of people gives engineer money to fix their dead phone, are you not tired of giving an engineer money to fix your dead phone? If you are tired then this is the best way to fix it by yourself. Firstly get a phone tools, disassemble the phone, remove the battery from the panel of the phone, bring out the panel  and solk a soft brush into a spirit or an alcohol. Use the brush to brush the panel softly and fix it back and also brush pins of the battery, Disassemble it back and that all.