Part 1 appears to be translated from another language, making it difficult to read. What is "that place"? How does it relate to the triangle ABC? What does "the distance from the place of the tribune" mean? What is a tribune angle?
Anyway, from the rest of the problem, to get you started: you know that triangle ADC is a 45-45-90 triangle. Since its hypotenuse has length x, the sides . Then,
Can you do the rest?