You are on a wrong track.
That is a PowerShell script. It has nothing to do with WinSCP scripting.
You have to execute that script standalone (like from a batch file or PowerShell), not from WinSCP script.
Example of the command-line needed to run the script is given on the script article:
https://winscp.net/eng/docs/library_example_two_way_synchronize_delete

Hello,
I want to use this https://winscp.net/eng/docs/library_example_two_way_synchronize_delete command in a script with the Windows 10 Task scheduler. But when I try it i get the error:

Script: Unbekannter Befehl „F:\...\SynchronizeTwoWayDelete.ps1“.

I want the command to automatically synchronize two folders. This should happen in the background and as efficiently as possible.

My script:

I would be very happy if anybody could help me because I have been trying for many days to get it to work.

Thank you