"On doit rester ouverts d'esprit."
Translation:We have to keep an open mind.
You're welcome! Another thing, why is it "....ouvertS d'esprit" and not "....ouvert d'esprit"?
There is a thread about this topic here: https://forum.duolingo.com/comment/27771879
And more detailed info here: https://www.frenchtoday.com/blog/french-grammar/understanding-french-on-subject-pronoun
IMHO both are correct. "On" can be "indefini" or personal. "One must be open minded", or "we must be open minded". The first translation is singular, the second is plural. We don't have a context to determine the intent.
What about "open-hearted"? (Earlier, "jeune d'esprit" was translated "young at heart.")
I think that "We must keep an open mind" is fine, as well as "We must keep our minds open".