Best fit article for you.. https://www.androidjungles.com/install-twrp-recovery-samsung-galaxy-j8-odin-tool/Still Need Help: You can ping me.Note: Do it at your own risk. I didn't test it.

It does not make any sense .. If you are playing high end game like PubG, please try with any stable WiFi connection. if problem still occurs, visit to the service center. They can flash your phone again.

You can uninstall pre install apps by following these steps - http://gigabyteedu.blogspot.com/2019/04/uninstall-pre-installed-apps-from.html

You can uninstall pre install apps by following these steps - http://gigabyteedu.blogspot.com/2019/04/uninstall-pre-installed-apps-from.html