So after a few days, here is what I learnt and what my strategy is now:
My bank DKB (where I have my checking account and which also offers a basic brokerage service) told me the same as most others of you reported: They don´t know anything about the deal yet and will inform me what to expect in time once they know more. Can´t really blame them, at least they replied within a day.
From what Elon said I expect him to set up something like they have for the SpaceX employees where Fidelity has a fund that includes only SpaceX which the employees can own IIRC. That would allow anybody to own TSLA private indirectly. For me I would have to make sure that my shares can get exchanged into that fund.
So the first point would be that my broker would support me owning this fund, which I am unsure of because they offer only a small selection of securities. So I am contemplating to moving to Interactive Brokers (IB) for example who seem to offer pretty much anything there is.
That brings me to the next possible problem: Where my shares are located. IB is located in the UK, so I guess by default my share would be held there? I still haven´t heard anything if this might really makes a difference. But to do everything I can it would probably be best to have them in the US. What does actually happen if I transfer my shares which I bought on German tradegate exchange to IB? Do they remain where they are (which depends on where I bought them as far as I understand) or move to the UK? Or could IB keep them in the US on my request?
Regarding timing, it sounds like opening a new brokerage account online and transferring my shares there should be a matter of two weeks or so. So for now, I assume I can still wait a bit until I make a decision.
With regard to the choice of my new broker, the main advantage of IB seems to be low trading fees which is important for people who trade very frequently which I don´t. On the other hand, they take a monthly fee if your portfolio is below 100,000 USD. They do definitely allow people from many countries to open account (unlike for example Schwab from what I read upthread). How do the other big international brokers compare? Might it be a good idea/is it possible to have your brokerage account directly through Fidelity, if they should turn out to be the issuer of the fund we might invest in?
EDIT: This is where I got the info about the structure for SpaceX employees:
Crosspost: Asked at /r/SpaceX for former SpaceX employee to answer questions relating to private equity and liquidity events. : teslamotors
Nothing official, but sounds legit to me, redditor seems to have a good reputation.