You can use something like this:

get /remote/path/* C:\local\path\*-%TIMESTAMP#yyyy-mm-dd-hh-nn-ss%

See
https://winscp.net/eng/docs/operation_mask
https://winscp.net/eng/docs/scripting#timestamp

how can i rename a file downloaded via winscp using only scripting, I want to add a timestamp at the end for date and time file was downloaded.

many files can be downloaded at the some time.