1. Take it to the tailor's shop and have it repaired by professionals.
2. Do it yourself, prepare two packaging belts that match the clothes, iron them with an iron, and then fix them with a needle and thread.
3. Fix a part with the thread matching the color of the skirt first, and then fix the rest after turning.
The above are three ways to replace the broken shoulder strap of suspender dress, I hope it will help you.