Custom field size

Hello everyone! Please, would somebody give me a hand? I’m having two main problems when customizing my Wpadverts page. The first one is that the description field is way two small and I need to increase it’s width. That way it would be easier to edit large photos in there. The best solution would be insert this field below the title (and not aside) so it occupies the entire screen area.

The second problem is that when I click on some item in the category list, a new page is opening containg all the ad’s from that category. But that’s not what I need. Basically, there are two widgets next to each other. The Left widget contain all the Ad’s ([adverts_list]) and the right widget displays all the categories. Is it possible to make the categories ad’s to load in the left widget area?

I don’t know nothing about programing, CSS and anything. Would someone explain me how to do that in a easy way?
ps: I’m using wordpress and Colormag theme

Thank you so much!