The bottom part of my screen doesn’t work so I can’t press the update

Sorry no, that's not possible remotely.

If your iPhone has a touch screen problem you won't be able to perform important processes like update, backup, restore, etc.

I suggest that you make an appointment (*) and have your device inspected at an Apple Store or AASP (Apple Authorized Service Provider) among this list:--> Apple – Location Selector. After checking it out, they'll give you all the available options.

Regards

Giulio

(*) You can do it:

• Online:--> Genius Bar Reservation and Apple Support Options - Apple;
• Contacting a local Apple Store or AASP among the list provided above;
• Using the "Apple Store" app, available and downloadable from AppStore.

Have you tried a forced restart?

This is done by:

1. Short pressing the Volume Up button.
2. Short pressing the Volume Down button.
3. Then, pressing and holding down the Power Button. Don't take your finger off the Power Button until the Apple logo appears.

If this doesn't work, post a reply here, preferably with a screenshot showing the problem.

Good luck!