I practically grew up in China. I usually stay in either Shenzhen or Zhuhai down south, but my favorite is Shanghai City.
Sentence structure wise, Japanese and Chinese are the same, but Chinese is a bit more difficult due to the details of pronunciation and similar sounding words.
I already know Chinese, but I rarely speak it since I never fully trained for that language.
So yeah, for me it's better if you know thr Japanese sentence structure already since it could help you learn Chinese.