i would like someone to enlighten me about the differences in astronomy&physics and philosophy&physics and how hard each classes are and careers opportunity after gradution.
You keep posting about things that you don’t need to decide about. You can of course read descriptions of the majors, which will tell you the differences in what classes you take. How hard the classes are will partly depend what you find hard and partly on the school you are in.
If you go into the general college (ie, not engineering) you will have up to two years to try all those courses and learn more about them.
As for careers opportunity, you’ve said elsewhere you want to be an astronaut. Or do physics. Or engineering. What is great about the US system is that you - as a give or take 18 year old- can explore these subjects and career options before committing to one. Pick engineering or physics and follow it for a while. Again: you will have more- and better- information to make your choices with.
Astronomy is an interdisciplinary science that is concerned with celestial objects - stars, planets, galaxies, moons, etc. Astronomy uses elements of physics and chemistry and has the potential to have lots of math. Physicists can certainly study astronomy (astrophysics is the branch of physics concerned with astronomy) and astronomers can use physics in their research. Physics is more generally the study of matter and its movement through space and time. There’s some overlap because a lot of physicists are concerned with astronomical concepts, but physicists can apply their work to a lot of different fields.
Philosophy is completely different. It’s the study of reality, knowledge, values, and existence. Philosophy is often called the mother of all sciences, since science in general stems from it - philosophical wonderings about reality and human existence motivated all scientific investigations and the invention of the fields of math, physics, chemistry, biology, etc. So philosophy can definitely have some overlap with science - and there’s a subfield called philosophy of science, in which philosophers study how humans create and process scientific knowledge. They also ask big questions - what is science? what is the purpose of science? Other philosophers may concentrate on ethics, which can extend to research ethics.
How hard each class is depends on you and your way of thinking. I find philosophy to be quite difficult because I am not good at abstract thinking. Some students don’t like the copious amount of writing that philosophy requires. I like math, though. However, a lot of students find physics and astronomy to be harder because they aren’t good at mathematical thinking or scientific thinking.
There are probably more job opportunities directly related to physics, or that physics can lend itself to, than philosophy. Physics majors usually have strong quantitative skills that can be parlayed in a variety of ways. Philosophy majors have to get a little bit more creative with what kinds of jobs they will consider and do, and need to acquire some concrete skills that will attract employers.