Hy,
Thanks for the courses first 
I couldn’t find the correct catagory for the course, so potentially that fits in here best. In Chapter 3 there is a hint to copy the URDF File of the two wheeled robot.
At least in my environment the proposed link doesn’t work:
/home/simulations/public_sim_ws/src/all/2wheeled/2wheeled_description/urdf/2wheeled.xacro
In my environment it seems to be:
/home/simulations/public_sim_ws/src/all/2wheeled_robot/two_wheeled_description/urdf/2wheeled.xacro
Just a hint.
Hello @mailenistdoof,
Yes, that’s an error in the notebook. I will fix it right now. Thanks for your feedback!