[3][4] The chef of the restaurant called Cheung Bo was a master of Wing Chun Kung Fu and began teaching him how to defend himself against his assailants.

In 1941, the famous Yuen Kay Shan owner of great properties in that state and winner of many death fights/combats, was introduced to Sum Nung.

[5] Sum Nung developed a great reputation toward the quality of his Kung Fu, he often had to fight to defend himself against the discrimination for being a foreigner.

The following year, he opened a natural (herbal) or traditional medicine clinic and was a Chinese doctor at Daisun Street and also ran a martial arts school.

The actor Zhang Jin was cast in the supposed role of Sum Nung, who was also an expert in Wing Chun and an able opponent of Ip Man in complex battles.