After selecting the text, you may tap Search button to search for the text from a relevant app on your device.
To translate the selected text, make sure that your device has at least one translation app installed, like Google Translate, DeepL Translate or other similar apps. Tap the Translate button and the translation will show up as a popover from your selected translation app.
If you need help on text selection, please refer to this article for more help: https://notewise.freshdesk.com/en/support/solutions/articles/150000151153-select-text-on-pdf-and-textbox.