Please keep an eye on your competitor, Monica. They keep upgrading their web page translation feature. When you click the "Translate" button, the whole web page gets translated automatically. Users can choose whether to replace the original text with the translation or add the translation below each line, kind of like a line-by-line translation. And with one click, you can easily switch everything back to the original. I requested this feature about a year ago, and even though they said you'd look into it, nothing has been developed yet.

Replacing the contents of a webpage is tricky business i.e. there is huge risk of this breaking the UI and causing a bad experience.

What you can do, is select text and use the Merlin Icon mount on the right edge of your screen. Hover over the Merlin icon, and it will show you features like Translate or Explain!