Hello, do you know how the language of a plugins is?
For the themes I know how it works but for the plogins I have struggled to do it since yesterday.

Chech this
https://osclasspoint.com/blog/how-to-translate-themes-and-plugins-b3

for the e plugin it does not work I tried everything for the themes its easy

@Alex
If it does not work, you did it incorrectly.
Problems are usually in following:
1) you've updated PO file manually via some editor and not PO Editor and/or MO file was not updated at all
2) translated PO and MO files are in incorrect location
3) using incorrect language code (folder name) for PO & MO files
4) incorrect naming of MO and PO file, that in themes is called theme.po, theme.mo; but in plugins is called messages.po, messages.mo

I had a hard time doing with the method you gave with the theme. to solve the translation problem of the theme I proceed as follows: I copied theme.po, theme.mo; and I paste them on file of the French language, it replaces (the theme.po, theme.mo;) of the original French language and then I do the manual translation. I record then I upload the language file to my site and it works. but for plugins (messages.po, messages.mo). I am stuck and I try everything then there is no tutorial for that.

I arrived after a great struggle. what i did i extract the us language file first then translate update and replace english with french and install the plugins and it works.

Nice to hear that