problems with the_author_posts_link()

I’m having troubles with using the the_author_posts_link() function in my wordpress blog. I’m using my titan-blog and that is causing troubles. I added the the_author_posts_link() to the description under the title of every post. This isn’t the problem.

The problem is: when you click on the link you get redirected to an automatically created author page. But this suddenly screwes up the whole design of the website. Even without using any author.php file or such a file, the author page looks fairly weird cause everything is enlarged a lot.

I’m quite a bit a WP beginner, and really can’t figure out what the fault is, but i’m expecting it to be in the css-file.

Some details:
the website (a Dutch website):
https://weerwatnieuws.com

The line in the index.php file which creates the link to the automatically generated author page:

<div class="author"><?php echo "Door "?><?php echo the_author_posts_link()?></div>

the css file (in which I expect to be the problem):
https://www.weerwatnieuws.com/?page_id=380

thanks a lot in advance! cause really don’t have any idea where to start…