Berlin recently introduced (or decided to enforce) a law banning landlords from offering short term rentals. The authorities are worried about the shortage of accommodation for locals. Air BnB has been badly hit. Landlords who ignore the law and get caught face enormous fines. My first booking was cancelled by the landlord. Fingers crossed my current booking doesn`t go the same way !
I did Paris last month. Not too fast but hopefully with better training Berlin will be a bit quicker.
I`m not a doctor so can`t answer that. I suspect you would be fine you should speak to an expert. Running at altitude when you`re not adapted is certainly very difficult. You will enjoy the event and perform much much better if you give your body time to adapt.