I deleted everything in my phone by mistake

Try to somehow reinstall the whole OS that your phone might be running (which means the right version of Android and for the correct device). If system files are missing, the phone will behave in a strange way.

This isn’t something that could be done easily, so I recommend just going to a repair shop which will most likely do that hard work for you. If they say it isn’t possible, or will require hard work and be very expensive, just buy yourself a new phone.

And remember to never touch the system files! If they are changed, the phone or even any OS won’t work properly!