it's my first question on this forum.
So don't hesitate to tell me if i am doing something wrong

I use Kile since several years now and never had this trouble : I am writing a document in french
and all the accents are displayed well in the .pdf output, when I compile with PdfLatex.
However, in the Kile editor my accents are sometimes swapped by weird Chinese characters.
So i erase them and put an 'é' for instance and then when i compile i've got "?" instead of my "é" in the .pdf file.
When I open the .tex file with another code editor (like gedit) i am able to see the "é" characters without trouble.
I am running Kile on Ubuntu 18.04 .
Do you have any idea what would be the origin of this trouble ?
Thanks by advance,
Regards,
Elie