Hello Issa,
This question is intriguing, not one I have had the opportunity to work through personally. I could see this being handled in different ways depending on the integration strategy (e.g. full integration vs. maintain separate businesses). As I’ve worked in an organization that had employee groups who spoke over 8 different languages, I can tell you that there was a sub-group in the permanent Communications workstream dedicated entirely to ensuring effective translation of all relevant communication materials (they had a very detailed matrix on what needed translation for enterprise-wide use vs. what could be developed and distributed by the regional business). There were multiple translators hired outside of the company on contract that did all of the translation to ensure accuracy with both wording and intent.