In Switzerland, up to 500 watts are permitted. However, there are various factors that are necessary for approval.
These can be read about here:
https://www.astra.admin.ch/astra/de/home/themen/verkehrsregeln/vorschriften-trendfahrzeuge.html
However, I would advise you to buy another product, because in my view Soflow unfortunately combines a bad product with even worse support.
The German translation of your question reads rather strangely. I don't know what a magnetic brake is, but I can say this: The brakes are the only thing on this e-scooter that is really bad. I just have problems with them. =(
The battery is permanently installed. Unfortunately you can't remove it, it has to be plugged into the bottom right-hand side of the scooter and charged. However, I thought this would be possible with the more expensive SoFlow models...but you would have to check again.
On downhill slopes, it can quickly reach 40 km/h. But then I recommend opening both eyes and ears very wide, because road users can hardly hear you and only see you late. It can manage gradients of over 15% at around 5-8 km/h. Anything over 20% is no fun and you will probably have to push rather than ride (depends on your body weight - 90kg as a reference).