why we dont have now a dinasour?

Answer 1

They were all killed when an asteroid struck the earth in Mexico and caused an enormous cloud of dust to arise that blocked the light of the sun for years. That interfered with plants and killed off many plants the dinosaurs had thrived on and also dropped the temperature below the point where they had the energy to move and get anything to eat.

Mammals and some more energetic descendants of dinosaurs (birds) survived and then flourished without the dinosaur competition.

Answer 2

We do. They are called birds.