geojulie
Just in case it can help anyone else, here is how I disabled Talkback.
First of all, note that the reaction time of the application is MUCH slower than your phone has normally. Also that green box is the FOCUS, and for example when your screen is locked, you can't just swipe like usual, you must tap on the little lock icon to move the focus there, and then DOUBLE TAP. Everything in Talkback seems to work with double tap to complete an action, so to navigate anywhere, you must first move the focus, then double tap.
After getting to the settings again, I found that I could not scroll down past what was showing on the screen, so I had to search for ACCESSIBILITY to access those settings. After which I could turn Talkback off.
As an aside, there are also some functions for Talkback that can be accessed from the lockscreen by swiping in an "L", but not an option to turn it off.
Now, if it doesn't work with Organic Maps, it will be definitely uninstalled.