Welcome to PF, Patridor!
Note: your thread has been moved to a more appropriate section of the forum.
Can you provide some clarification on what you mean by "what should I do as a job?" Are you thinking of your long term, "permanent" job (i.e. career) that you will take on after completing your university education? If so, then what does "making my options for my exams in year 11th" have to do with anything? Or are you asking about what to do for a more near term job, like a summer internship, or something? I'm not aware of too many opportunities for research that can be carried out by people who are still in high school, but it's worth looking into. Someone should definitely give you "the talk" about what academia is like, and the reality of your prospects for being able to continue as a researcher all the way up to the faculty level (hint: few people make it this far). You'd be in it for the long haul (a PhD, at least). If that doesn't deter you, then maybe you can start thinking about what kind of research you'd like to do.
If you're asking about careers, then I would say that you will have plenty of time during university (after doing some actual summer research, ideally) to decide whether you prefer doing astronomy or some other field of physics. For now, just focus on working hard and doing well in your courses and exams, particularly math and physics.
We can't decide for you what you should do as a career. We can only make suggestions based on what you tell us about what you like, which is not that useful. At the end of the day, it has to be your decision, based on what you are passionate about.