depends on where you're talking about has campaign and FW have different requirement for 3 stars

Im the campaign part last 3 on each cant get 3 

i

assuming you're having trouble meeting these requirements, can you post your roster, see if we can't help you out?

also which difficulty are you trying to beat?

Thanks thats what i 

I want to add, that the term "without losing a champion" may lead to a misunderstanding. Both champions have to be alive at the end of the stage, but if one of your champs is a reviver, you can absolutely lose one champion during the fight, as long as you manage to revive that champ.