One of the problems with learning app development is having something on which to focus. Come up with an app idea (doesn't have to be overly complex or unique) and start writing.

You might also find a topic that interests you and work on an open source project in that area, like I did with Resolver and Factory, two dependency injection libraries I created on GitHub,

You might also checkout my profile, as I've written quite a few articles on iOS development and SwiftUI over the years. Some of those might be of help.

Good luck.