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>