Why my phone not update

Which of these large tasks do you wish help with first? Can't you possibly narrow down the issues a bit?

Your Apple ID isn't working:

Click on this link to read what to do "If you forgot your Apple ID" --> https://support.apple.com/HT201354 Note that typically this is an email address you use.

Click on this link to read what to do "If you forgot your Apple ID password" --> https://support.apple.com/HT201487

Your iPhone doesn't work:

is it turned on? In what way does it not work?

App Store not working

Again, many possibilities here, particularly that it could be related to either of the above.

Won't update:

If you see an error when you update or restore your iPhone, iPad, or iPod, click here --> https://support.apple.com/HT201210

If your iPhone, iPad or iPod touch won’t update - "You might be unable to update your iPhone, iPad, or iPod touch wirelessly — or over the air — for one of these reasons", with more detail in this link. --> https://support.apple.com/HT201435

" Not enough available storage space on your device

Downloading the update takes a long time

Unable to reach the update server

The update doesn't complete"

If you need more space for an update - https://support.apple.com/HT203097

Things to try:

Plug your device into your computer to update using your computer.

Delete content from your device and try to update again.

Manage the storage on your device with recommendations.

If you can't update or restore your iPhone, iPad, or iPod touch - You can put your iOS device into recovery mode, then restore it using Music/iTunes.

https://support.apple.com/HT201263

Any exactly quoted error messages would likely speed up a possible solution.