I selected a “4 week” completion track for UXA Foundations, but I believe it’s actually going to take me longer. Is this a problem?

No! This is not a problem at all, and just because you select an estimated track in which you’ll look to complete UXA Foundations does not mean that you are locked into doing so. You’re not bound to completing the coursework in a set amount of time, regardless of what you indicated when signing up. Additionally, taking longer (or shorter!) than what you stated initially will not impact your application to UX Academy, as long as you finish UXA Foundations within the 8 week timeframe given for the course.