TL;DR : Go here and download this app (while it's available).
Earlier this week, we saw FileGo leak on the Google Play Store but it was quickly taken down. FileGo is specifically built to help users (even novices) manage and clean files from their devices (duplicate photos, application cache files, etc).
FileGo also contains a function (similar to Apple's AirDrop) that allows Android users within close proximity to transfer files to each other.
FilesGo is still beta software (aka it could still have bugs) but in my testing has been reasonably reliable and hasn't crashed yet (tested on a Nexus 6P and Note 8).
Keep in mind that Google can change user eligibility once the app is officially released (may be limited to Android One users or restricted to certain regions) but right now it seems to be available to all users globally.