Please correct my mistakes.

请改正我的错误。

youdao

Please correct my mistakes when I speak to you.

如果我有语法错误的话，请你纠正我好吗？

youdao

My Chinese may be not so well, if you find any mistakes of my Chinese, please feel free to correct them. I will be appreciated of your help.

我的中文也许不是很好，如果你们发现了我的错误，尽管纠正我，我将非常感激你们的帮助。

youdao