What were the difficulties and dangers of the merchant’s activities in the Middle Ages?

A merchant in the Middle Ages could have such problems:

The robbers. They could be land-based, that is, hide in the forests, mountains and steppes along the way, there were enough such places in Europe and Asia, so it was not difficult to rob a merchant. Sea robbers (pirates) sailed in different seas, in Europe they could be Normans (Vikings, Varangians), Arabs (south of the Mediterranean, for example, Algerian), as well as pirates in the Indian Ocean and off the coast of China.
Greedy rulers, feudal lords and others. They often fought with each other and could rob a merchant.
Epidemics. A merchant could contract, for example, the plague and bring it with him to his hometown.
Competitors. The merchant could go broke.