CSS menu help (twenty eleven)

Hello,

At the moment I am working on http://www.woonerfbreughelhof.be

But I am running into trouble getting the menu CSS like I want it to be.

1)I basicly do not want the activated link to be able to hover over again to the black…

2)Also is it possible to only have an underlined hover under the text lets say instead of the full text.

3)How do I get rid of the “gradiënt overlay” it only shows in Firefox & Google chrome.

4) Can I change the height of the menu bar? If so how can I do this in my CSS.

I hope someone can help me with this.