how to delete extra words?

In index.php look for,

<?php the_time('l, d. F Y'); ?> von <?php the_author() ?> <?php edit_post_link('**', '&nbsp;&nbsp;', ''); ?>

You can see the “von” and “admin” is generated by <?php the_author() ?>

This will occur on all pages that contain posts, not just index.php

Exactly the way I just showed you. You can see the word “von” in my previous reply – delete it. As for the worth “admin” I already said it is generated by <?php the_author() ?> – delete it. (or replace it with something else if you wish)

If you open up header.php you will see this,

<div id="kopf">
<h1><a href="<?php bloginfo('url'); ?>/"><?php bloginfo('name'); ?></a></h1>
</div>

That means your blog title is contained within the div called “kopf” and uses the <h1> tag. Armed with that little nugget of knowledge we go to your style sheet where we find,

#kopf h1 {
    margin: 0;
    padding: 0 20px;
    height: 120px;
}

#kopf a {
    color: #fd5;
    font: bold 20px 'trebuchet ms', arial, sans-serif;
    text-transform: uppercase;
    letter-spacing: 1px;
    line-height: 120px;
}

This block defines the styling for anything using the ‘<h1>’ tag within the “kopf” DIV, in this case your blog title. Under “#kopf a” delete the line “text-transform: uppercase;” This says if h1 is a link make it uppercase.

Edit: oops, missed the first part of the question. Yes deleting <?php the_time('l, d. F Y'); ?> will get rid of the timestamp.

I deleted the “text-transform; uppercase;” but the blog title is still in all caps.

Refresh your browser, you’re probably looking at a cached page.

all the titles on the sidebar (Pages, Categories) are all caps

Open sidebar.php. You will see <div id="seitenleiste"> which means everything is contained within the DIV named “seitenleiste”. Headings in this DIV use the <h2> tag as you can see here >>> <h2><?php _e('Pages'); ?></h2>. Once again we go to the style sheet. Look for,

#seitenleiste h2 {
    margin: 5px 0;
    text-transform: uppercase;
    background: url(img/kopf.gif) no-repeat center center;
    padding: 1px 5px;
    color: #fd5;
    font-size: 11px;
}

This says any <h2> tag within the DIV called “seitenleiste” shall be uppercase. See the relevant line? Are you starting to see the logic of style sheets and how they work?