Here is what you need to do:
Locate your GarageSale 6 Library
In your account’s home directory (the one with the house icon), go down this path
Library > Containers > com.iwascoding.garagesale > Data > Library > Application Support > GarageSale
(If you don’t see the Library folder in your home directory, you need to make it visible by using the “View” menu > “Show View Options” command.)
Copy and compress library files
From that “GarageSale”-folder, copy these items (if present) into a new folder you created on your Desktop:
GarageSale.sqlite
GarageSale.sqlite-shm
GarageSale.sqlite-wal
AuctionImages
Upload library
Name the new folder appropriately, e.g. “GarageSale-6-Library-from-Jandro”, and compress it into a .zip folder (right click on the folder icon).
Go to this webpage and upload your .zip file:
https://www.dropbox.com/request/WWrEke7GlgfevssLOIvY
Depending your library size and internet connection, plan in an appropriate amount of time for uploading.