You might try this for some entry level reading 
A few things to check out. Can you find your way to Recovery mode, do you have TWRP installed?
What Android version are you on.
Is there a choice of unofficial builds available to you?
Do you have the option and/or do you want to upgrade Android version? That option will require some reading.
Do you have the option and/or do you want to update /e/ version. Much easier, still requires reading!
Do you have a Windows or a Linux PC available for the work? There is quite a lot of overlap in methods for Windows and Linux, but a big source of confusion if you are new to this and you flip flop between methods!
Bon chance
Edit. @db_p did you see this thread with some history of your device on /e/? I see that I failed to include the link. 