Yongnam is more of a construction company which is cyclical in nature. In the investment quadrant course, you are taught to invest in predictable companies. The thing about investing in cyclical companies is to know when the cycle is at and only purchase it at the bottom. It is hard to understand the cycle if you are not industry player.
Regarding exit strategy, is your initial analysis of Yongnam still valid, if yes, you should continue to hold on to the stock with conviction. If not, than probably you should switch out to other more predictable company.