permalink: category and page in a menu

<ul id="menu">
<li><a href="<?php bloginfo('url'); ?>">Home</a></li>
<li><a title="Copyright information" href="overons/">Over Ons</a><li>
<li><a title="Copyright information" href="watwedoen/">Wat We Doen</a><li>
<li><a href="<?php echo get_category_link($blog_category_page); ?>">Blog</a></li>
<li><a title="Copyright information" href="contact/">Contact</a><li>
</ul>

Above is my menu. You can see it in action here. I have just set up permalinks, and try to figure it out. It works good, as long as I stay on pages, once you click on ‘blog’ it links to https://www.mysite.nl/blog/category/blog/ since my blog is a category and not a page (I do not know how to set it like a page…). When you click on a page like contact from ‘blog’, it tries to reach https://www.mysite.nl/blog/category/contact instead of https://www.mysite.nl/blog/contact, and comes up with a 404.

Is there a way to fix this? I do not know how. pherhaps with some sort of ‘if category’ command? I am puzzled!