As I said before, they are image assets. You can find them under the image folder(e.g. game\images\buttons). And they can be translated by replacing them. You can edit them in Photoshop or some other photo-editing software.
Another thing is that, plz inform the devs that your specific language. It is not Chinese, but Simplified Chinese or Traditional Chinese. As a player, it should be fine; but as a translator, it should be strict.
Have fun translating!