Section 1299 ABGB describes two groups of cases. A person who publicly presents themselves as holding an office, practising an art, trade or craft must stand behind the necessary knowledge and diligence. The same can apply where a person voluntarily takes on a task that requires specialist knowledge or unusual diligence.
For private skiing, the actual assumption of responsibility matters. A short comment such as “bend your knees” or “slow down there” does not automatically turn a friend into a professional instructor. A person who plans a longer exercise, chooses a difficult descent, sets the pace or line, or expressly presents special expertise may have taken on a more demanding task.
Section 1299 ABGB also refers to the inexperienced person’s knowledge. If the learner knew or could have recognised the friend’s lack of experience with ordinary attention, that fact must also be examined. The provision supplies neither automatic liability nor a free pass. It directs attention to the task assumed, the knowledge on both sides and the concrete error.