auto populate textbox1 when selecting values in combobox

Dear All
in textbox8 i will enter number that wan to add column C in sheet2
and want to add unit beside this number (if i select Kg they will add kg to number in the cell,
if i select L they will add L as unit to number in the cell)

in textbox2 the data want to populate automatic as the following
when i select date in datepicker2 according to product name selected in combobox1
and shelf life time for this product from sheet (Ref) in column W they will add this number as year to date selected in picker2
for example if i select 19-7-2017 and shelf is 2 the date in textbox2 will be 19-7-2019 and soon


auto populate tetxbox6 from selection of combobbox2 from column S and related in T column



textbox5 want to enable to when i press it , it open window to brows the computer to look the file
with extension photo or pdf
then


when i press add data to sheet2 will add all to corresponding cell and attached file browsed