I have a question: I made all the 3-star challenges but I didn't get the trophie. So I checked the leaderbords and I wasn't on the Be More Objective leaderbord, though I made it twice! doe anyone know how this comes?

You have to complete all of the 3-star challenges using the same character. The easiest way to do this is to make a new character and keep them below level 5 (level 1-4=rank 1) as enemies scale to your current rank. Good luck.