===== Android =====

https://opengapps.org/

https://twrp.me

https://lineageos.org/

Fastboot:

On your device, go into Settings -> About and find the Build Number and tap on it 7 times to enable developer settings. Press back and go into Developer Options and enable USB debugging. From your computer, open a command prompt and type:

  fastboot oem device-info
  fastboot devices
  
to check, if device is recognized. 

To flash TWRP:
Download the to your phone matching image file on https://twrp.me/Devices/ and copy the file into the same folder as your adb and fastboot binaries. Rename the image to recovery.img and type:

  fastboot flash recovery recovery.img
  fastboot boot recovery.img

You should now be in TWRP Mode.

Just reboot:

  fastboot reboot
  
Useful commands:

  fastboot flashing unlock
  fastboot oem device-info

ADB:
  
  adb devices
  adb logcat
  adb shell
  adb reboot bootloader
  
You should now be in fastboot mode.

Problems? Check FW and adb driver!

Flash:
  Dalvik/ ART Cache
  System
  Data
  Cache