what will happen to us when we die?

Physically, we're embalmed, put in a box, stuck in the ground, rot, become bug food and eventually turn into nothing. Spiritually, your guess is as good as anybody's. Maybe we go to heaven. Maybe we fly around the universe. Maybe once we're gone, that's it. Who knows? Religions claim to know, but the whole concept of faith is that you don't know for sure but believe something anyway. So you can believe whatever you want.