Sounds like you have something on the phone (virus, malware, bad app, etc.) that is causing the problems.
If this is the case you have a few things you can try...
1. Just restart the phone (power it fully off and then back on). This may resolve it.
2. Uninstall the app(s) that are giving you issues, restart the phone and then reinstall the app(s).
3. Check the phone for viruses and malware (they are not the same), removing any found, restart the phone and see if the issues are resolved.
4. If none of this fixes the problem, then you may want to consider backing up all your personal stuff to another device (files, contacts, etc., but not apps, can't back them up) and then do a full "Hard Reset" of the phone to restore it to its original status prior to using it.