Before Yo starts farting, Gerd is standing to her right, instructing her. After Yo's first fart, he is suddenly next to Gunter on her left.
With the amount of gas Yo has stored up inside her, she would have felt her fart attack coming beforehand, yet she shows no sign of discomfort until it actually starts (no stomach pain, bloating, stomach growling).
Tiffany's position as Yo models is directly in between Yo and the camera, meaning she would be blocking the shot.
The "spider monkey" Gerd refers to is actually a capuchin monkey.