Was lange währt, wird endlich gut – is a German play on words: what lasts long, will at last be good. If something takes time, even a long time, it will most likely turn out just right.
In the context of agreements having to wait a longer time for the deliverables of that agreement is worth it, worth the wait. Patience pays, pays off.
Geduld bringt Rosen – patience brings roses – or Rom wurde auch nicht an einem Tag erbaut – Rome wasn’t built in a day – or Steter Tropfen höhlt den Stein – steady drops of water hollow out the stone – are German figures of speech conveying the same message. Even if it takes a little longer, ….