I used to do English to Chinese translation jobs on Upwork, the pay was reasonable (translators are very under-paid in China) so there were some good translators. Nowadays Upwork are much more hostile to freelancers (or just Chinese freelancers?) and Chinese translators are leaving the platform.
You should be able to easily find a freelancer by asking any Chinese people. Just look for someone who speaks very good English. Incompetent translators usually don't understand what they're translating.
Also, I suggest you to spend time communicating with your translator, instead of simply providing an excel. Translators need to know the context of the material they're translating. If they're translating a game, show them the game, if they're translating the app, show them the app and explain to them what it does. Or they will make hilarious mistakes. For example, "The Elder Scroll" was once translated to Chinese as "Old Man Scrollbar", "Lord of the Ring" as "Lord of Horse Racing Track".
You should be able to easily find a freelancer by asking any Chinese people. Just look for someone who speaks very good English. Incompetent translators usually don't understand what they're translating.
Also, I suggest you to spend time communicating with your translator, instead of simply providing an excel. Translators need to know the context of the material they're translating. If they're translating a game, show them the game, if they're translating the app, show them the app and explain to them what it does. Or they will make hilarious mistakes. For example, "The Elder Scroll" was once translated to Chinese as "Old Man Scrollbar", "Lord of the Ring" as "Lord of Horse Racing Track".