Looping itab into another itab with mandt

Hello I have a itab(itab_data) that contains data such as first name, last name, role, etc... and I am trying to put that data into another itab(itab_sy) with client(MANDT) in the first column and SY-DATUM, SY-UZEIT, and SY-UNAME in the last columns.

I am unable to populate all the system variables the same time as the rest of the data because I am uploading a excel sheet into itab_data.

I have tried to append line of itab_data to itab_sy and tried a nested loop however the client variable is giving me the most issues. How can I create an itab with SY-MANDT, firstname, lastname, role, SY-DATUM, SY-UZEIT, SY-UNAME. When I already have the middle data in another itab?