If you stir-fry fresh Spinach, a lot of water would come out of it, and the water has unpleasant taste. I strongly recommend to blanch Spinach before you stir-fry it, so that you won’t have the unpleasant taste, and also you can reduce oxalic acid that can cause health problems. This is a very simple dish. You can use more Spinach and Pork, and alter the amount of Oyster Sauce accordingly.