Answer:
1. because of the tilted axis of earth the seasons in northern hemisphere are the exact opposite of the southern. because the sunrays reaches the earth an different points and when the earth moves around the sun it changes the hemisphere which is tilted to the sun.
2. the northern hemisphere is in Winter and the southern in summer. because the southern is tilted to the sun and the northern not so less sunrays reaches the northern hemisphere.
I'm sorry my explanation are bad