what am I doing wrong?

I got this Nexus tablet to travel with but I can't work on my files with it. Mostly it just won't open things. When it does open things, everything is apparently read-only. I have tried four different apps: "document viewer," naturally only for viewing: kingsoft office, which a friend of mine uses to edit just fine: android office: and android open office.  There is just no responsiveness at all: I can view the text, and scroll around in it -- but the onscreen buttons don't work.

These are files from dropbox and google drive, and only the .rtf ones, not the .doc ones. The .doc ones produce a grey field where the text should be. When I was trying this with kingsoft, I got errors with .rtf, but the docs would open.

I have spent hours and hours and hours on this. I am actually heartbroken. The whole point of spending money I didn't have was to edit my files while I am traveling.