Ok, good work. If you set a width on your horizontalNav, for example 200px, you can subtract that as well as the margins of the info DIV.
left-margin = 25px, right-margin = 25px, horizontalNav = 200px. De info Div has a width of 49%, so what’s left = 51%, right?
So the aside should have a width of 100% – 49% – 200px – 25px -25px. So that would be: calc(51% – 250px). Then the 3 of them will fit nicely next to each other.
And you can wrap the images on the top of the page in 1 DIV to prevent them to appear on top of the other content. There is a lot of siblings in your page while its better and easier to style when you try to group elements in kind of sections.