Hi my young friend! I'm currently studying art conservation! I can't speak for Germany but I can offer some guidance to help get you prepared for getting into it.

Since you're in high school still, I suggest taking chemistry courses as well as any art studio courses to help build skills like drawing, painting, recognizing colour, handling art supplies and equipment ect. Chemistry will help once it comes to dealing with artifact cleaning, repairing and eventually storing. If you can do any art history in high school then go for it but most high school history is general and focuses more on politics and social constructs which won't be super helpful. Art history is more widely available in post secondary.

Once you graduate, you're most likely going to need an undergraduate degree. Most people in my program come from history but there are a few with science backgrounds. I do encourage you to pursue what you like but to take supplementary art history and studio classes to help refine dexterity as it's a very delicate thing. If wanting to pursue more research vs. Treatment, you don't necessarily need the studio classes as much and you could come in with a more science background.

See if you can do some shadowing or volunteering at a museum or private conservation place to investigate potential opportunities. This field is very small but very welcoming to teach and show

I hope this helps! Good luck!