There are a lot of translation APIs available, but I don't know which ones can be used freely (or affordably, as the case may be).

https://www.programmableweb.com/category/translation/apis

This one lets you choose Microsoft: https://addons.mozilla.org/firefox/addon/jxl-page-translator/

After installing, go to the Add-ons page to select that. Either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons
• type or paste about:addons in the address bar and press Enter/Return

In the left column of the Add-ons page, click Extensions. Then find Page Translator on the right side and click its Options button. Scroll down to the bottom where there's a selector to change from Google to Bing.

In the same place, you also can set its icon to always appear in the address bar (just left of the reload button) instead of only on non-English pages, in case you are viewing non-English text on a mostly English-language site.

Reload the page you want to translate after changing settings.

Note: I only tested for 5 minutes, so I have no idea how reliable it is.