is there any solution to open properly the xml files within konqueror ?

I believe if you right click on the display area, you can switch to using embedded KWrite which will display it correctly.

thank you , id like konqueror displayed them like firefox does
as you say we can display correctly the xml in kwrite

KWrite can be embedded in Konqueror, which will allow Konqueror to display Xml files correctly.

How i can do this ?

Konqueror should do it by default. You can check by opening System Settings > Advanced > File Associations. Expand "xml" and switch to the "Embedding" tab. Use the controls to move "katepart" up to the top.