Yes. Messages you write inside a demand are translated automatically and reach the other side in both the translated and the original wording.
When a message is written in a language other than yours, the Messages tab shows the translation first. Tap Original (IT) underneath it to reveal the sender's own words, and Hide original to collapse it again. The translation never replaces the original — both stay side by side.
The same dual display goes beyond chat: the demand description on the Details tab and supplier notes in the Offers list are translated and shown with their original text too. Every free-text field that travels between buyer and supplier is covered.
It works in both directions: what you type appears to the other side in their language, and your own sentence stays one tap away.
If the text is already in your language, or no translation is available for that language pair, no extra line appears — you simply read it as written.
Also asked as: are my messages translated automatically? · how do I deal with a supplier who writes in another language? · can the other side see my original wording? · is in-demand messaging bilingual?