Have you used revision control to make any snapshots ?
OK The assets and thier positions should be alright, the problem is the landscape.
Using revision control and snapshot history would make it easier, but if you haven’t got any snapshots its a little bit of trial and error to find the landscape assets in the project folders.
If you have revision control on, the first thing to do is Move your islands project folder from User/Documents/Fortnite Projects to somewhere else on the hard drive like C:\projectTemp
Then load UEFN and download the latest backup.
If you haven’t done a check-in with revision control for this project, we need to identify the landscape actors in the project files.
Depending on which scenario your at there’s a few options