Is it a good user experience to have multiple languages on the same page?

I am working on a new challenge. Is is a global site with multi-language support. My task is to design a support portal that will be in English only. This same support portal may also pull in portions of the site such as product pages. Due to the site architecture, which is massive and not going to change, the user will still be in their originally selected language. So for example, if the user selects French, the site will change to English, then if any product pages are pulled in they will be in French, with any portal information displaying in English.

I am still trying to wrap my head around this concept. I've looked an I didn't find any related posts, if there is one I will gladly move this discussion. If there are any questions I will gladly answer them.

Which brings me to my questions: Is it a good practice to have multiple languages on the same page? If not, what is better? If so, are there any best practices or practical examples?