unit 2.2 past simple met onregelmatige werkwoorden

in the past simple irregular verbs have a own mold you must learn from your head. that form you can use for all subjects.
just look:

i                     had    a friend                             ik                        had           een vriend

you                had    a friend                             jij/u                     had           een vriend

he/she/it        had     a friend                            hij/zij/het             had           een vriend

we                  had    a friend                            wij                       hadden     een vriend

you                 had    a friend                            u                         had           een vriend

they                had    a friend                            zij                       hadden     een vriend

for the irregular verbs overview you should look in your text book