Unable to select folders for upload from iphone, only files

I'm looking to upload a large collection of photos and videos from my iphone to Dropbox, but they're all stored within the Files app instead of the Photos one. I've added Dropbox to the Files app and have tried to click and drag the files to Dropbox but it says I don't have enough space on my iphone to do this. Freeing up the space isn't an option because it's a rather large amount of photos and videos, and freeing up space is the reason I'm trying to do this in the first place. 

I have attempted to use the uploading option in the Dropbox app itself, but it doesn't allow me to select folders, only files. And selecting each file individually isn't an option because we're talking about thousands of photos and videos seperated into a bunch of folders based on dates, events, etc. Trying to just copy the folder in Files and paste it into Dropbox only gives me an Empty folder, and when I attempt to hold click on the main folder in Files, click share and then "Save to Dropbox" the Download button that appears stays gray and unclickable no matter what I do. I have plenty of storage space available on Dropbox so that shouldn't be an issue either. 

I went with Dropbox because it has proven to be easier than iCloud for me to access and manage files related to school and work from my PC as well, but if I can't get this phone stuff to work then Dropbox isn't going to be an option for me.