The fist problem anyone reading the English translation runs into is Byington's choices as a translator. Stirner is tweaking the nose of German Romantic (and anti-Romantic) sensibilities by provocatively quoting the first line of a work by Goethe, whose poem was paraphrasing the first line of Ecclesiastes.
The German word *sache* means any number of things, including "thing" but also "affair," "business," "matter," "job," "story," "question," "cause," and "subject."
In keeping with a more modern anarchic appreciation of Stirner, I would translate the sentence as "All Causes are nothing to me."