Woocommerce noob

Hi all… again.
https://www.agrohol.com is my site. There are 3 things i can’t figure out.
1. Removing the grey border around my thumbnails in my catalog.
I posted in the forum before, but no one helped me ??
I read the FAQ’s of woocommerce. There was exactly that question.
The answer is”Install firebug, inspect the thumbnail, edit your custom css with the code bellow as an example.

.entry img, img.thumbnail {
  background: none;
  border: medium none;
  padding: 5px;
}

But i have no idea how the work with firebug. And of course
I have no idea from where to edit my custom css. I tried from the wordpress editor – nothing. And i can’t find what i need in the .css files in the woocommerce folder. My eyes started to hurt after staring it for something like 2 hours.
2. I have no idea why my catalog align looks like sh*t. I spent few hours looking at this and guess what – nothing.
3. I added few images in my product gallery. Is it possible to add arrows to it? So that the users can click to see next image (like on facebook or something like that) without having to press “go one page back”and click another image.
Please everyone, i really need your help on that. Those are my final things i must to before I can say – hey my website is ready.
I usually post here only after i tried for hours via google or FAQ’s.
I’m begging you help me.