I will try to add my two cents, which might help you a bit. I do not consider apple documentation easier to dig into either, however, I am more than sure, more experienced users will say it is much more user friendly now than it is used to be :).
Maybe it is easier to start your search using this link https://developer.apple.com/documentation/technologies
So here you will see different libraries that exist in apple. For example, if you need to dig into more basic things you can refer to Standard Library of Swift Framework https://developer.apple.com/documentation/Swift .On the left side you will see links to Int, String, Array, etc.
Should you need find info on Array properties and methods you can look into this: https://developer.apple.com/documentation/swift/array Which inlcudes functions such as dropLast, dropFirst, sort etc.
For SwiftUI framework you can dig info here https://developer.apple.com/documentation/SwiftUI etc. I think you got the point.
Sometimes it is not so obvious that structure has some method. E.x. you won't see func filter on Array or String by following above links. But if you scroll all the way down on String or Array on the detail side (right side). You will see section Relationships and Conforms to. So this part is Protocols which those structures conforms to, and Sequence protocol has method func filter, so that is why both String and Array can use filter method...
Ugrrrhhh, I know... what the heck.... But this is how it works. BUT no worries with more practice and coding days you are getting used to such things and you will learn what methods are available to different data types. So keep coding and keep learning.
AND sometimes it is just quicker to goole what you want to do and find info :)