I cant translate the strings "Secondary Groups" and "Default Avatar" because I can't find the string in Loco Translate or in the Phrase Editor.
With best regards,
We've added these phrases in next wpForo Update. Currently, you can add missing phrases in wpForo phrases system. Navigate to Dashboard > Forums > Phrases admin page, search for those phrases again, if you don't find, click on [Add new] button. Insert the phrase key the identical English version and the phrase value your translated version and save it.
More info in doc: https://wpforo.com/docs/root/translation/quick-translation-phrases/