Dear Radmila,
first of all, thank you for the purchase!
this is exactly why the footer is not being fixed in most of WordPress themes – including mine – if you fix it, it will always stick to the bottom of the window, not the bottom of content – and if the content is larger than the browser window, it will show over on under the footer, which is of course not very good-looking. There’s no logical way to have both, so I’m afraid you will need to choose: either fix the footer on the page (but it will overlap the content sometimes) – OR let the footer stay in the natural flow of the elements (then it will not show up at the bottom of the page unless you don’t have enough content on the page). Based on my theming experience, I would recommend the second way, which is also used in the majority of all WP themes.
Sincerely,
Andrii / Satori Studio