I will answer auf Englisch, if that's OK.
(1) I am just about to buy some STEEM, partly because it looks like a stable investment, partly so I can power up and - as a newbie - increase my visibility on the platform. I am only waiting for the right moment in the market.
(2) Like you I believe strongly in Steemit and believe that it is a wonderful thing IN PRINCIPLE. How long, and how well, it will survive depends on whether it can be saved from the minority of people who seem to be subverting it for their own selfish (money-making) reasons. Decentralization is great but it shouldn't be worshiped as a god: we need restrictions (different from censorship).
(3) In 10 years? That's a long time in this world. Maybe. But if not Steemit, something else that will allow people to get an audience for good content and get rewarded for it, without the consumer being bombarded with ads. Anyway, in 10 years time I'll be 73 years old so I probably won't care! :o) It will be up to your generation to make it succeed.
Namasté, Nici.