me again.

So I wonder how to change the size of headlines?
I tried to change it in using the override.css. I did a few things using the override.css and it is working. But not the headlines.
I'd like to have h1 - h6 in a smaller size. So I reduced the count of px. Uploaded override.css in the right place, but nothing happend.
So, what did I missing? (1. at screenshot)
Another question about headlines:
If I choose a category or a post, the new side appears and below the menu area the headline of that category, tag, page or post appears in white letters. The slider is pushed down a little. How can I stop that? I don't want that appearing. (2. at screenshot)
Thanks for helping!!!
cheers
Alex