Answer and Explanation:
They travel together because they are very close friends who have known each other for many years and Henry's father believes that it is a good idea for them to spend time together as a student and become more cultured, in addition to being distracted.
Victos' return was postponed because he had a very high fever, became very ill and had to recover to endure the trip back to Geneva. Vitor only returns when he is completely recovered, but he managed to spend a good time while he was away.