Try using ADB & Fastboot. Connect your phone to your computer with a USB cable. Hold the power button and volume down button for a couple of seconds. This should open a menu where you can select factory reset, recovery etc. Don't select any of the options here (just leave as is for now).
Now, you will need a computer for this next bit. Download the official ADB & Fastboot binaries from the following links:
Windows:
https://dl.google.com/android/repository/platform-tools-latest-windows.zip
Mac:
https://dl.google.com/android/repository/platform-tools-latest-darwin.zip
Now you will need to download a custom recovery (preferably TWRP) and flash the recovery.img file using the ADB shell. To do this, place the downloaded recovery.img in the main folder of fastboot (the zip you downloaded earlier) and type 'adb devices' in the ADB shell window and you should see a 'List of attached devices' with a code (your device code) underneath. This is just to verify that adb has detected your device.
Type 'fastboot flash recovery recovery.img' and wait for this to finish. Once it has, try booting into the recovery again and you should be able to make a backup of your phone using TWRP (note that TWRP backups do
not backup your personal data, only system and app data). Backup your personal data onto your computer.
Once that backup has been created, you should restore that backup and put your personal files back onto your phone.
After all of this, your phone should work again! 😃
This took me a while to write (I had to do it on my phone) so I really hope it helped. 😊 I hope you managed to fix your phone. - InferiorBeing