There seem to be an error in the tone placement for i and u, such as for niu (cow); jiu (alcohol) etc
Hello, thanks for your post! 
Would you mind telling us more about the course that you are learning so that we could look into it?
If you can send me an email ([email protected]), with screenshots (including course, level etc) that would be great!
Best,
Yi
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hi i have sent you an email. thanks