Not sure of your condo layout, but is a door possible at the top of the stairs? I found out long ago, that temp gates don't do much with larger dogs if their goal is to get to the other side. I think I've gone through about 3 gates so far.
Had my pup pinned into the laundry room at my parents place one day when visiting and used a 5ft "gate". Sure enough, came back that evening and he was walking around the house.
I still don't know how he accomplished this. And this was with a bum hind leg at the time.