我係後面架喎...
I was standing behind...

Cantonese Sentence Breakdown

我 ngo5
I
me
my
us
we
our
self
係 hai6
(Cantonese) to be
to connect
to relate to
to tie up
to bind
to be (literary)
to involve
relation
relationship
consequence
yes
indeed
right
後面 hau6 min6
behind
架 gaa3
to support
classifier for planes, large vehicles, radios etc
to prop up
fight
quarrel
喎 wo6
a final particle to express surprise
agreement
disagreement
tone of reminder or emphasis
when quoting words said by others