I tried the first solution, but since the people have more tasks in the same period assigned them, to put them as 100% per task has a result of people shown as overloaded in the resources diagram, I thought there is a simpler solution in Project for that...
Im sure Im not the only one having the issue that people assigned to projects do accutualy as well other things than to work only on the project... but this is more a topic of accurate planning and as well about a conflict of theory and praxis