Theoretically, it is possible. They both belong to the Latin family. It is not a problem for people who speak two languages to communicate with each other. They know each other's language differences, so they can make a correct judgment based on years of experience, even if they are completely different.

An interesting example is that now we are learning Spanish, and the teacher won't let us watch Italian TV programs, because we still can't hear the difference, and we are always afraid of getting confused.

As for Cantonese and Mandarin, I think there is a big difference. There should not be many people in the mainland who can understand Cantonese.