If you want to do a factory reset of the Dopo M975, ifixit has instructions. View the question, Why does my tablet keep freezing?
This will erase any data on your tablet.
I also found a tutorial on youtube that shows how to change the language to English, that may help you. You could view other videos with similar titles that might be closer to what you're looking for as well.
Lastly, page 19 of the manual has a screenshot of the English menus that you could use the respective icons to Navigate to the language menu that can help complement the video I referenced.
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