Yes. I know, it was just to show how the adress looked like even if the page was the index.
I now have this in my sidebar:
<?php wp_get_archives(apply_filters('widget_archives_dropdown_args', array('type' => 'monthly', 'show_post_count' => $c))); ?>
And this in my archive.php:
https://pastebin.com/pa2f4fwt