My Apple ID does not sign in

When I try to sign into my Apple ID, it asks me to input my username and password, once i do that it comes up saying "signing into iCloud" or something along those lines, and then after a few seconds it just takes me back to the page on settings where it says I need to sign into Apple ID.

My problems began back in december, when my phone randomly turned off and wouldn't turn back on, I took it to the apple shop where they plugged it into a computer, worked their magic and updated my phone. At this point in time I thought I was okay, but when it came to signing in to my apple ID after the update, it would put me into the loop as stated above. The woman helping me told me to keep trying over the next few days and if nothing happens to back my phone up through itunes and then completely factory reset it, then restore from the back up and everything should be okay.

Through laziness I just lived with not being able to use my Apple ID, until earlier today the version of my whatsapp ran out and I couldnt use it because i needed to update. So i've done what she told me to do, and it hasnt worked. And to add insult to injury all of my apps begin to update and then freeze because they cant finish due to no apple ID, meaning my phone is now completely useless now.

PLEASE HELP ME!! 😟