Take a photo of your completed exercise. Post it to HelloTalk or Tandem and ask: "Kann bitte jemand meine Hausaufgaben korrigieren?" (Can someone please correct my homework?). Native speakers love helping with this. It is 100% free and more valuable than an answer key because they explain why you are wrong.
Instead of looking for Kursbuch answers, the user should utilize the officially free resources which are legal and accurate. menschen kursbuch a12 answers free
If you stop searching for "free" and start searching for "legitimate," here is how to actually get the answers. Take a photo of your completed exercise