The Thunderhooves level is wrong. It told me to do 10 meters below/above the yak, but it turns out it has to be 5 meters or else the yak hits you before you can place the fence.
oh yeah, I remember that, I had to usde 5 meters too, but that was with Okar, you need a fast hero, but they are required for subscription
You may want to contact someone like @nick
Or, you could contact Bryukh