To administrate your Xirvik seedbox from your iPhone you may use an app called BarMagnet.
Unfortunately, BarMagnet is not available on the Apple App Store, so you will have to sideload it. This page will show you how to do that with an application called Cydia Impactor, which works with Windows, Linux, and macOS.
Please note that you may have to reinstall the app every 7 days due to limitations with iOS code signing. However, thanks to the QR code system, setting up the app each time is very easy.
Also, if you have a jailbroken iPhone, you may be able to use a jailbreak tweak to install the IPA from https://github.com/Qata/BarMagnet/releases, but this has not been tested.
(Windows screenshot source: shoutpedia.com)
Thankfully, setting up BarMagnet is a lot easier than installing it.
BarMagnet is a very simple app to use once it has been installed. In the main screen of the app, you can see a list of your currently active torrents, with some important information:
If you tap on a torrent, you can see much more detailed information about it. Also, there are buttons to pause/resume the torrent, and remove it:
You can add a torrent by tapping the + icon in the top-right. Or, conveniently, you can tap on a magnet link in Safari, and it will be added.
Please note that if the torrents list appears blank, you may just have to wait 10-15 seconds for BarMagnet to load the list from the server.