This support is absolutely genious. Thanks so much! 

Add this CSS code to the custom CSS

#wpforo #wpforo-wrap .wpf-field input, #wpforo #wpforo-wrap .wpf-field input, #wpforo #wpforo-wrap .wpf-field input, #wpforo #wpforo-wrap .wpf-field input, #wpforo #wpforo-wrap .wpf-field input, #wpforo #wpforo-wrap .wpf-field input, #wpforo #wpforo-wrap .wpf-field input, #wpforo #wpforo-wrap .wpf-field input, #wpforo #wpforo-wrap .wpf-field input, #wpforo #wpforo-wrap .wpf-field textarea, #wpforo #wpforo-wrap .wpf-field select {
  padding: 3px 4px 3px 32px !important;
}

Dashboard > wpForo > Settings > Colors & Styles > Custom CSS

And read this topic >> wpForo and Cache Plugins

can someone help me solve this problem?

As you can see in the screenshot, the font awesome icons cover my textfields. I would rather see them at the right side of the textfield. I managed to change it in Chrome Console, but at WordPress it doesn't seem to accept my change in CSS.

In wpforo settings, i just find an option to deactivate them, but that's not whhat i want.

Can anybody help me?

Thanks a lot