Portrait mode
How can I get portrait mode for my iPhone 7device
iPhone 7, iOS 15
You don't, sorry.
These iPhone models support Portrait mode: iPhone 13, iPhone 13 mini, iPhone 13 Pro, iPhone 12, iPhone 12 mini, iPhone 12 Pro, iPhone 12 Pro Max, iPhone SE (2nd generation), iPhone 11, iPhone 11 Pro, iPhone 11 Pro Max, iPhone XR, iPhone XS, iPhone XS Max, iPhone X, iPhone 8 Plus, and iPhone 7 Plus.
Extracted from:--> Use Portrait mode on your iPhone - Apple Support
Regards
Giulio