How do I click a button and show only one category?

Only one problem left.

I have links in my header using this code

<li class="bk1"><a href="<?php bloginfo('url'); ?>/?cat=Home">Category 1</a></li>
<li class="bk2"><a href="<?php bloginfo('url'); ?>/?cat=Gallery">Category 2</a></li>
<li class="bk3"><a href="<?php bloginfo('url'); ?>/?cat=Don't Vote">Category 3</a></li>
<li class="bk4"><a href="<?php bloginfo('url'); ?>/?cat=Ammoz">Category 4</a></li>
<li class="bk5"><a href="<?php bloginfo('url'); ?>/?cat=Fiction">Category 5</a></li>
<li class="bk6"><a href="<?php bloginfo('url'); ?>/?cat=Empires">Category 6</a></li>
<li class="bk7"><a href="<?php bloginfo('url'); ?>/?cat=About">Category 7</a></li>

etc.

However, when I click on the links in the header it still shows posts from all categories.

How do I set it up so that when I click on a link (in this case a picture) in the header it shows me only the posts from a certain category on the main page?

Thank you again