Welcome to FT, Johannes, and make a mental note that posting the same question on multiple threads is a big no-no.

I would suggest the moderators move your request to the "Miles Buzz" forum, where "beginners" are welcomed and your question can be addressed.

Meantime, it will be important for you to think about your detailed flying patterns, whether you fly on paid business fares or cheapest economy, etc. - the devil is always in the details.

Good luck!