I tested this RDFa on Google Structured Data Testing Tool:
<main vocab="http://schema.org">
<article typeof="NewsArticle">
<h2 property="headline">Wie instaliert Virtual Box in Windows 10</h2>
<span property="name" value="Virtual Box"/>
<span property="mainEntityOfPage" value="http://google.de"/>
<span property="datePublished" value="2019-03-07"/>
<span property="dateModified" value="2019-03-17"/>
<span property="publisher" typeof="Organization">
<span property="logo" value="https://schema.org/"></span>
<img src="http://htmlkurss.xyz/index.php/Bilder/Virtualbox.png" alt="Logo"/>
</span>
<p property="text">Virtual Box ist eine Virtualisierungssoftware, die viele Betriebessysteme ,...
</p>
<p property="author" typeof="Person">Autor: <span property="name">ich</span></p>
<p>Korrekturen: <span property="editor">me</span></p>
</article>
and the SDTT tells me that
logo.itemtypehas an invalid value
logowithtypeof="ImageObject"(!) inside ofOrganization. – unor Mar 14 '19 at 20:11