In our multi-method study, feedback levels derived from the well-known feedback model of Hattie and Timperley were used in conjunction with feedback that was related to subject-specific content; here, mathematical reasoning tasks in primary school. Feedback needs to be aligned with the learning process; in the beginning, more task feedback is valuable. Based on the analyses of videos and questionnaires of 44 teachers of 5th- and 6th-grade primary school classes (N = 804), we demonstrated that feedback for finding an approach and operationalisation were related to feedback on the task. We further showed that feedback at the task level predicted students' achievement in mathematical reasoning via students' interest in mathematics. It might be concluded that the four levels of feedback should be applied by teachers in such a way that they focus on the current problem that is occurring while the student is solving a task.