[NSIdk]

Okay so my phone won't start up. Like it won't go beyond the company logo. I had this problem before too but I somehow got it to work. When I did get it to work, I thought I'd back up my stuff but there was no file manager? Then all the apps in my phone storage stopped working so I had no other option to try to reboot aaaand I'm back to square one. It won't work. My friend had a similar problem and she got told it's android glitch and they downgraded the system+factory reset. OKAY BUT. I managed to get to recovery mode and there is the user data back up option, right? NOW HELP ME OUT HERE-

1. IF I WERE TO BACK UP ALL THE USER DATA IN A SD CARD, WHAT ALL DATA ARE WE TALKING ABOUT?
2. DOES THIS REALLY WORK? IS THERE ANYTHING I DO ALONG WITH IT?
3. DO I FACTORY RESET AFTER? WILL IT DO ANYTHING IF IT IS AN APPARENT ANDROID LOLLIPOP GLITCH?
4. WILL MY APP DATA BE STORED IN THE SD CARD TOO? I'M PRIMARILY CONCERNED ABOUT THE WHATSAPP CHATS.

PLEASE PLEASE HELP ME OUT I HAVEN'T USED MY PHONE IN 3 DAYS I'M GOING CRAZY

[thesims2customs]

What's your phone? I think you're having bootloop, I use TWRP (Custom Recovery) and it does have backup option, it could backup the system, data, image, kernel, etc..
I never have seen a problem like this before, BUT if your concern is Whatsapp chats, it is okay to factory reset, since Whatsapp would backup the chats everyday and backup it up to Google Drive (if you don't disable it).