Alexa connected rollershutter kinda inverted via voice commands

That’s because your voice command is interpreted as “increase” and not “raise”. The former increase the current state value by 1%. While the latter would send an UP command.

Make sure to use these utterances:

Alexa, fahre die Rollo hoch. (Raise)
Alexa, fahre die Rollo runter. (Lower)
Alexa, öffne das Rollo. (Open)
Alexa, schließe das Rollo. (Close)