I’m trying to update my phone and it’s not working I can’t press the download and install button cos it doesn’t work

There has been sufficient advise / suggestions offered form several well informed Contributor.

How to check the storage on your iPhone, iPad, and iPod touch

The update needs to download, expand and then install. If the iPhone does not have enough Empty Space - the pda will never download at all

If, as you claim it does not work after checking or making Empty Space , Find an Apple Authorized Service Provider or Visit a Genius at an Apple Store

You will need an Active and Stable WIFI CONNECTION

Connect to Wi-Fi on your iPhone, iPad, or iPod touch

Update your iPhone, iPad, or iPod touch

You need to connect to WiFi, not a hotspot. You also need to shut off low power mode.

Hello ~ In addition to *P. Phillips* advice your iPhone is in Low Power Mode. Toggle that off.

Use Low Power Mode to save battery life on your iPhone or iPad

~Katana-San~