Best ways get up to speed on the structure of an existing Quickbase business app?

Have you at least located the Relationship Diagram tool found under the app management table under settings for the app.  The first step is to drag and drop that to unscramble it.  

Tip #1.   Be sure to click save as you go from time to time but most importantly before once you have it unscrambled.

Tip#2. Try to get as many of the lines uncrossed as possible and turn off the label for ghe reated parent field.

Tip#3. when that annoying popup comes in the middle of the screen, drag it way don to the corner somewhere.