Hi Digigumball:
There are many ways to accomplish what you’re looking for and how you have contracted the page layout as well as the field structure of your setup in EE will have a lot to do with the advice you are given.
In terms of the width of the text area to stay clear of the image - that’s a tough one. Since the image is a background, it doesn’t interact with the text, which is an inline element. And your background image changes orientation based on the dimensions of the viewer, so it would be very difficult to plot a relative position or sizing for that container that would keep the text from overlapping the bottle.
In terms of changing the text within the body area of the page from quality, benefits and buy content, it comes down to how you have your fields setup in EE. Are each of those product-related paragraphs in their own fields within a single product entry? If they are, then you could simply load them on the basis of a url segment. You could get a bit fancier with it with javascript/ajax if you want the content to load without the url changing, but just out of the box with EE, loading the content based on an additional segment at the end of your url for benefits, for example, would be simple.
Hard to be more specific than that without knowing more about your setup. Hope this helps.