In order to coach at the highest level of German professional soccer one needs a license, which is obtained after completing rigorous theoretical and practical training. Once obtained, the professional soccer coach is granted the official title of Fussballlehrer, literally soccer teacher. Not coach. Instead teacher.
Like a school teacher who has given a test, the soccer teacher (the Germans use the term Trainer) has very few levers during the match to influence its outcome. He must hope that his players apply during the match all that they learned and practiced.
The coach (formally Fussballlehrer, informally Trainer) and his staff work with their players on technique, practice specific strategies and set plays, try out different formations. But once the match begins the coach can make only three player substitutions, can to a limited degree yell certain instructions to the players, has only a few minutes at halftime to provide instruction. In the end, therefore, it is the players who have to know how to react to the opposing team.
The coach is practically a bystander. In fact, the rules of soccer prevent too much communication between coach and players during the match. Again, the coach is like a school teacher, who can only hope that his students have paid attention in the classroom, have done their homework conscientiously, and will apply during the examination what was taught to them.