In French, médecin and docteur mean both doctor, but they are used in different situations. You use médecin to talk about the job, while you’d use the word docteur as someone’s title.
Je vais prendre rendez‑vous chez le médecin.
I will make an appointment with the doctor.
Le médecin appelle le patient pour prendre de ses nouvelles.
The doctor calls the patient after the surgery to see how he is doing.
Le docteur Phil est un animateur télé.
Dr. Phil is a TV host.
Docteur, est‑ce que ce médicament a des effets secondaires ?
Doctor, does this medicine have side effects?
You’ve seen how to form the future for verbs that end in ‑er and ‑ir. For regular verbs that end in ‑re like vendre or attendre, you will keep the ‑r from ‑re for the conjugation and use the following forms:
Elles vendront leur maison.
They will sell their house.
Tu attendras la réponse.
You will wait for the answer.
Vous perdrez votre tour.
You will lose your turn.