All the documents you will be asked to sign will be in French, and often contain legal terms that you may be unfamiliar with. You may find a notaire who speaks some English, and some agents offer translations of the compromis de vente (although this is not their primary role or responsibility). If you are uncertain about any aspects of the contract, you can obtain a professional translation either within France or in your home country. Ask the agent if they can recommend an independent translator (and remember to add the translation fees on top).