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if you haven't signed an "Unterlassungserklärung", you may be sued, even if you paid. Things may get mor expensive if you cannot prove or at least explain in detail that it wasn't you who offered protected content for upload.
Even if it wasn't you, it would be recommendable to sign an Unterlassungserklärung (with a few mods from the form used by Waldorf) to reduce the risk of litigation costs. This should be at least supervised by a lawyer.
AND: Make sure that no illegal content will be shared again. Else it will get even more expensive.