Transfer video files between Windows PC and iPhone XS for external app being offline

Hi,

I'm struggling to transfer quite big video files from my Windows PC to an iPhone XS having no Internet connection (I'm in travel, only mobile data which I can't use for movies sharing via iCloud).

I need to transfer some video files from Windows PC to the iPhone and then be able to edit these movies in an external app on iPhone (InShot).

I've tried:

1. Transfering with USB cable and iTunes. I can transfer a movie to "Films" section in iTunes on Windows, but then I only see that movie in "TV" app, I can't find it using InShot
2. Transfering using EaseUS MobiMover - same effect as in point 1.
3. Transfering using dr.fone app - same effect as in point 1.
4. Transfering using http://web.xender.com/ - doesn't work at all, even being on the same WiFi network it's interrupted straightaway (I guess the files are too big).

Again, such simple task, why can't it be done with drag-and-dropping files using Windows Explorer like with all other devices in the world...? I would expect 1400$ phone to be able to do such crazy stuff.

Thanks a lot for your help!