App starts loading at first use?
The app requires for additional files to be downloaded, video files in this case. This is a one time occurrence.
Is there an Android version?
Why yes, yes there is: https://play.google.com/store/apps/details?id=dk.crmarketing.slimfit30_0&hl=en_US.
How do I cancel the subscription?
This can be done within the app, or by following Apple instructions, available at: https://support.apple.com/en-us/HT202039.