The most important thing related to this duel is that Geralt can't use Witcher signs and bombs. You must defeat only a single opponent during the training - Prince Horm Akerspaark of Maecht. Go with Guillaume to the arena and stand in its central point. This step will activate only if during the conversation with Guillaume you agree to train for the melee battle competition. If you fail an attack, then don't try stopping or going back to the obstacle - you don't have to destroy them all to guarantee reaching the finish line in time limit. Only then you can be certain that the dummy is correctly hit.
What's important, during the race you can gain additional seconds by destroying the obstacles on your way. You must travel through the track (the green line on the minimap) before the time ends. This step will only activate if during the conversation with Guillaume you agree to train for the horse race competition.
Example objects to attack with the sword and with the crossbow
