Is it as simple as showing up with the extra check-in luggage and paying the 80-100 euros for it?

I read some blurb (when buying the ticket) that I can't buy extra baggage, because of the FRA - WAW continuing flight? (Something about that it might be full, iirc).

Just wanted to ask about this, as I wasn't exactly sure of the process from the Condor website (to avoid surprises at the check-in counter)