We are planning to travel from marseille fr to barcelona in sept need advice bus or train?
For buses, look at http://eurolines.com/en/ For trains, look at this to get routes and schedules: https://www.ricksteves.com/travel-tips/transportation/trains/online-schedules. To get prices, you'll need to use http://www.tgv-europe.com/. Select Great Britain as your country and France as your ticket collection country, and refused to be redirected to Rail Europe. For flights, look at http://www.skyscanner.com/
Booking the train will be an adventure. No one seems to be able to book both the Spanish and the French trains.