Welcome to Android Central! Try the steps here on how to do a factory reset with the hardware buttons:
https://www.lg.com/us/support/help-...0-ms323-device-reset-CT10000027-1395196443010. Be aware, though, that this will probably activate Factory Reset Protection, and if the reset is successful, the phone will still prompt you for your friend's Google account and password to proceed. Hopefully he'll help you log back in.
In addition, the Optimus L70 is 6 year old phone, and as far as I can tell is stuck on KitKat (although there are custom firmware available up to Nougat, but that would require rooting the phone). KitKat is quickly becoming incompatible with many major apps due to obsolescence, so be prepared for that.
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