So SOO many issues

[Alex.A]

First question: is your phone up-to-date? Are you using the stock OS? If yes, you should have a version number named 19.11.2.

@Chayyes

The power button is I believe stuck as it won’t show the lock screen (this is with both the case on and off)

Is the button itself on the motherboard blocked? In this case, bad news, you need a new motherboard (or you can try unblocking the button somehow).
But how do you boot the phone then? Maybe it could be a software issue?

@Chayyes

But before that my phone would randomly freeze the screen and go on multi colourd striped rampages or screen image multiplications.

Did you check these topic?
Fairphone 2 touchscreen suddenly freezes
Noisy coloured pixels on my Fairphone 2

@Chayyes

I also have to use headphones to take phonecalls for the screen not to go black and for the reciever to hear me.

This should be easily solvable. Go in the settings→Maintenance→Proximity sensor calibration, and follow the steps.

@Chayyes

My camera or camera app doesn’t work and don’t know why as I have plennty of free storage space.

How exactly doesn’t it work? Does it crash? Does it fail to capture photos?
What happens when you use another camera app, e.g OpenCamera (F-Droid and Play Store)?