"It was our common choice."
Translation:To był nasz wspólny wybór.
In Polish, there exist both words starting with "współ-" and some starting with "wspól-" - all of them mean something referring to "common".
The difference is that "współ-" is just a prefix (like English “co-") added to words that also have a meaning on their own ("współautor" = co-author, "współwłaściciel" = co-owner); there are many such words in Polish. There are also just a few words that have the adverbial prefix "wspólno-" (meaning “commonly-“).
The rest of words starting with "wspól-" are words that all seem to be derived from the noun "wspólnota" (unity, community) - there are not many such words, in a large dictionary containing over 455000 Polish words I found just 15 of them.