UITableView fixed section with dynamic size

I am trying to implement something like this:

I have a UITableView with 1. "static" section, the total number of sections in the tableView can vary. I always want the first section (white area) to be visible to the user, the remaining sections should scroll underneath the first section. I have tried to implement this with two UITableViews, but since the (white area) can vary in size, I can't set a definite frame. I am using Storyboards with autolayout. At the moment the best solution I have come up with is the two UITableViews, but I need to find a way that I can resize the two tableViews according to the content of the white area and according to each other. The white area, one of the tableViews is containing a section with two rows, the first row is containing text that can vary in length and therefore needs dynamic resizing. Any Idea how I can tackle this? Can I change the NSLayoutConstraints dynamically somehow?