According to this Apple Support Article, I should be able to easily delete files from the File App on my iPhone in iOS 11. However, when I select a file anywhere in the File App, neither "Delete" or the Trash Can icon are available as explained in the article.
iMac with Retina 5K display, macOS Sierra (10.12.5)
I just figured it out. On the iPhone UI there is "Select" at the top right. Click that, and then simply tap any file(s) and there is a check mark added to them, much like selecting a photo in Photos on the iPhone. Only then, does the trash can appear at the bottom right of the UI. Oddly, there is absolutely nothing on Apple.com explaining this. Just glad I stumbled onto the procedure.
It wouldn't show up in a screen shot, I'd have to do a screencast and it's not worth it. It's very simple...the support article says "Select the files that you don't want anymore and tap Delete or click the trash can icon". Neither of these exist, so the file can't be deleted from the Files app. When you select any file in the Files app, that file is simply opened, and from the opened display it can not be deleted. I tried it on three different iPhones using iOS 11 and it's the same. Try it using any iPhone using iOS 11 and you'll see what I mean.
That’s the first thing I tried. When I long-press on any file icon it opens the file temporarily. Then when I release the long-press, the open file collapses back to the icon. You must be doing this on an iPad...try it on an iPhone. The interface shown in your screenshot doesn't exist for either of my iPhone 7's.
Have you tried a long-press? From the context menu showing up you can select "Delete".
Can you post a screen shot of what you are seeing?
How to take a screenshot on your iPhone, iPad, and iPod touch - Apple Support
How to delete files from File App in iOS 11?
