Got the problem, thx @Nils Nolde.
My Problem was a misunderstanding of the multipolygon structure.
[[[
["8.22252","48.84632"],["8.22267","48.84622"],["8.22280","48.84629"],["8.22263","48.84643"],["8.22252","48.84632"]
]],[[
["8.22996","48.85469"],["8.23086","48.85438"],["8.23133","48.85480"],["8.23013","48.85531"],["8.22996","48.85469"]
]],[[
["8.23468","48.85407"],["8.23459","48.85296"],["8.23601","48.85251"],["8.23674","48.85392"],["8.23468","48.85407"]
]]]
What I had:
[[[
["8.22252","48.84632"],["8.22267","48.84622"],["8.22280","48.84629"],["8.22263","48.84643"],["8.22252","48.84632"]
],[ // <= One Layer of Arrays missing
["8.22996","48.85469"],["8.23086","48.85438"],["8.23133","48.85480"],["8.23013","48.85531"],["8.22996","48.85469"]
],[ // <= One Layer of Arrays missing
["8.23468","48.85407"],["8.23459","48.85296"],["8.23601","48.85251"],["8.23674","48.85392"],["8.23468","48.85407"]
]]]
It is now working.