I do that, but nothing happened

The Files are in: ftp: wp content/plugin/wpforo/wpf-language

Ah, i just figured out the German Translation is empty. It seems we've not German language, those files are not translated. You can translate using free Poedit. Open wpforo-de_DE.po in Poedit, update new phrases and translate. After saving translation you should upload and overwrite the both .po and .mo files. It would be great if you share those files here, we'll add in next release.

I started to create german translation files. Most translations for message textes and dashboard are not ready but the normal users will see german textes. In the forum statistics is a problem with 2 textes. It seems to be that there is no matching phrase in the po-file you attached in this topic. I marked it red in the screenshot.

In the Top/Menu Bar I have the problem that I translated it in the po-file, created the ro-file, uploaded it in the right folder but the Top/Menu Bar is still in English.

Edit: Wenn I'm ready with the translation files I can send it to you @Robert

Menu Translation

Please read this topic:  https://wpforo.com/community/faq/how-to-translate-forum-menu/