store_url does not render link correctly

Add store direct_url instead of store_url

<a href="{{store direct_url='produkte/insektenschutz/fenster/spannrahmen.html'}}">

spannrahmen.html will show after this.

Try adding this to your block:

<a href="{{store direct_url="produkte/insektenschutz/fenster/spannrahmen.html"}}">Link to Base URL</a>