1. Retraction update: When the main branch and the side branch are retracted, the back branch and the upright branch with smaller angle and stronger growth are selected to replace the original head.

2. The branches should be shrunk again: all kinds of branches should be cut again, more and less sparse, and the angle should be improved.

3. Renewal and rejuvenation: more pruning and less vertical branches, promoting branching and enhancing growth potential.

4. Reduce the number of layers: reduce the number of layers as much as possible, reduce the height of the tree, and increase the illumination in the inner room, so that it can obtain strong branches that are updated at all levels.