Phone keeps hanging on Joy Plus 3

I have an Oppo Joy Plus and last week my phone keeps hanging whenever I opened an app like facebook,instagram or opera browser some app can open but some don't,for ex. if I opened instagram it will open for a few seconds but then it freezes and it says either instagram is not workinf or the OS launcher is not responding,I already format it but still it won't work,when I scan for antivirus it says there's a malicious app and force to stop it,the app is com.android.os. PLEASE HELP!