This sounds like your LGs Home Launcher has glitched.
Go to Play Store and see if there is another option as a launcher. Try searching the apps for Nova Launcher, then download and install.
Let me know how it goes please.
Okay, the only other option will be to do a hard reset using the hardware keys.
Try these steps please.
Remove the battery, then reinsert the battery.
Then with the phone powered off.
Press and hold these keys at the same time.
Hello and Welcome, my name is Michael.
I would like to give it another try to find the right solution to your issue.
Go to through the same procedure BUT DON'T release the POWER KEY until the factory hard reset screen displays.
Please let me know if any further questions on this matter.
if you need any advice in getting a replacement for the phone, the me know and I'll be happy to help.