> Officially change my name?
Yes. That's the only one that's going to actually work. You can go on about how these systems ought to work until until the cows come home, and I'm sure plenty of people on HN will, but if you actually want to get on with your life and avoid problems, legally change your name to one that's short and ascii-only.
in the meantime he was unable to own the company he founded (instead made his wife the owner), had a national ID card with a different character, and i am not sure if he had a bank account, but i think the bank didn't care because laws that enforced the names to match the passport/ID only came later. i don't know how the ID didn't automatically imply a name change, but the IDs were issued automatically and maybe he filed a complaint about his name being wrong.
Sort of but not really. The post-2012 residence cards do not display a registered alias anywhere, and since those cards are what banks are required to KYC you on, a lot of banks won't allow you to use a registered alias which in turn means it's hard to use it for anything else (credit cards, phone, pension...). It's very non-joined-up government.