Hello manuel9010,
Thanks for using Apple Support Communities! It looks like you're having trouble with Portrait mode on your iPhone 7 Plus, and we'd like to help.
Has your iPhone 7 Plus been previously able to take Portrait mode photos and also see them as Portrait mode in the Photos app?
If so, have you restarted your iPhone since noticing this issue? If not, go ahead and do that, as a restart can resolve unexpected issues. Restart your iPhone
When you're taking the photo, make sure you're using the rear camera, as the front facing camera on an iPhone 7 Plus doesn't have Portrait mode as an option.
Check out the steps in this article: Use Portrait mode on your iPhone