Swift Api, resuming downloads and dealing with large files?

Question

iOS

I'm currently learning how to work with the internet and trying to understand the trail of things.
1. If the file is large, how can I download it better? (as I understand it better in parts, then the question is to write it yourself, is this mechanism or is there a ready-made server on node js, and as I understand it, the mechanism should be on both the server and the application
) paused or disconnected? (and what should be on the server side for this)
3. If I pause dataTask, does it break the connection with the server or not?
4. If I have URLSessionConfiguration.default, then when the application is minimized, what happens to the request and should it be paused? (how the application should generally behave in such a situation)
5. if I set the download in the background, can I change something in the controller through the main thread after the download is completed, despite the fact that the application is minimized?