<iframe class="videoplayer" src="https://player.twitch.tv/?channel=saphir3xDjWeiga&parent=https://projekt-takeover.de&parent=localhost&parent=ni483264-1.web20.nitrado.hosting" height="478" width="850" frameborder="0" scrolling="no"></iframe>
should be
<iframe class="videoplayer" src="https://player.twitch.tv/?channel=saphir3xDjWeiga&parent=projekt-takeover.de&parent=localhost&parent=ni483264-1.web20.nitrado.hosting" height="478" width="850" frameborder="0" scrolling="no"></iframe>
You have a https at the start of one of your parents