[AngelicaDeAlquezar]

Your answer would be correct, depending on what you want to say:

"Mientras viajaba aprendió mucho sobre la cultura de la gente" means that during his/her trip (one-time event), that person learnt about people's culture.

"Mientras viajaba aprendía mucho sobre la cultura de la gente", means that he/she would learn from people's culture every time he/she travelled (a habit).