The iOS update is taking way to long!

Hi, you can force restart your phone:

iPhone 8 or later: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then press and hold the Side button until you see the Apple logo.

iPhone 7, iPhone 7 Plus: Press and hold both the Top (or Side) button and the Volume Down buttons until you see the Apple logo.

iPhone 6s or 6s Plus: Press and hold both the Home and the Top (or Side) buttons until you see the Apple logo.

Check this: Update your iPhone, iPad, or iPod touch

Switch Off Low Power Mode and connect iPhone to power.