How can i define the "DOWNSTREAM" in a especific bend?
You don't really need to think of "up" or "down" stream. Think of the "in-coming" tangent and the "out-going" tangent.
How can i especificate the bend angle in the piping imput?
You don't.
CAESAR II determines the bend angle from the direction cosines of the "in-coming" tangent and the "out-going" tangent. This is why it takes two elements to define a bend, and they must be sequential elements.
What´s the meaning of each one of them (Angle 1, Angle 2, Angle 3)?
If you want to have additional node points on the bend, you specify the desired node number, and the angular location (in degrees from the start of the bend).
The graphical overview show a bend out of phase of the entire piping system.
Chances are you're putting other elements between the two tangents. Don't do that. I suggest you refer to the bend description in the Quick Reference Guide - that should help clear things up for you.