Due to the 'greater than' you have to use the LOOP instead of the READ Statement.
Make sure the ITAB is defined as SORTED or HASHED TABLE.
Maybe it is an Option to first delete all entries from ITAB where F3 <= SF-F3.
Then you can use the READ Statement instead of the LOOP.
You have to verify with SAT-Transaction which Version is the better one for your case.
Make also sure that the ITAB structure only contains fields you really Need in further processing.
Having an ITAB with a wide structure and millions of entries will also slow down Performance.