New feature of Gmail, in this you can change the language to any language

Click on the 'Translate' option to change your email language 

If you understand the language of the mail, then you can remove the option of translation

   You can bring back the translation option by clicking on the three dots 

Now you have to choose the translate option here

Now you have to choose the language in which you want to translate the mail

Your mail will now be translated into your preferred language