I can’t download Firefox on my IPhone 11 can you help please?

Hello,

To download Firefox on on iphone, just go to the app store, search for Firefox, and tap the Get button to download the app. After that, you can tap open to customize Firefox to your preferences or Sync.

Firefox requires iOS 15.0 at minimum to run so you should be able to install it on the Apple App store on your iPhone 11 if you kept the iOS updated.

https://support.mozilla.org/en-US/kb/firefox-available-iphone-or-ipad-my-language

Notably, you have submitted this question from a current version of Firefox iOS, so unless the question related to another device, you're all set here.