@martin

Thanks, I have now (thanks your reply) made an Q&A forum and give it the name 'forum'. But in wpforo/wpf-themes i see only "classic". And I cannot choose another theme in the wpfora dashboard

@ger
There is no Q&A theme. The Classic theme has four layouts. One of them is the Q&A layout. Please click the link Martin provided and read the documentation. Forum layouts can be set to certain parent forum. Saying parent forum i mean forum in Dashboard > Forums admin page not the whole forum on your website.

@martin

Thanks Martin, finally everthing is working fine. But I have the same issues as 3 years ago. I cannot translate a lot of phrases with Poedit, simple because of that the phrase aren not in the .po file and not in the .pot file.. And adding a phrase is also not working for me.
I'm afraid that the conclusion is that i cannot use this fine forum.

@ger,
Yous should not use Poedit, just use the loco Translation plugin:
https://wordpress.org/plugins/loco-translate/

If your forum is not multi-lingual you can translate all front-end phrases in wpForo Phrase system, just edit and change the value of phrase to the translated version. If you don't find any phrase, click on [Add New] button, add the identical English version as phrase key and the translation version as phrase value. More info: https://wpforo.com/docs/root/translation/quick-translation-phrases/

So, wpForo has no any issue with the translation, more info in doc:
https://wpforo.com/docs/root/translation/how-to-translate/

@robert

I did this: If you don't find any phrase, click on [Add New] button, add the identical English version as phrase key and the translation version as phrase value

But doesn't work for me. And why not Poedit?

@ger
Nobody says you must use wpForo Phrases, use whatever you want, but Poedit can be a bit difficult so you can install Loco Translate plugin and translate in dashboard instead of use some software like Poedit.

That's your choice. If you need a quick translation you can use wpForo Phrases, if you need PO/MO files you can use either loco Translation plugin or Poedit. Loco Translation plugin or Poedit based on PO/MO files.
In other words you can use whatever you want if your website is single language website.

@Robert

Thanks for your reply.
I have probably done something wrong. But wpforo Phrase works now.
If I now create a forum on a different domain can I copy the translation?

@ger,
Sure, you can. You can export wp_wpforo_phrases table in Hosting > cPanel > phpMyAdmin Database management Tool. Then delete the same table from target WordPress database and import the exported (translated) one.

@Robert

Thanks