On Desktop things will flow naturally, however as the screen size decreases, each element will need a size declaration for the css to push full width, or they will shrink within their own space. Add 100% or 100VW for each element you want to push across. This will force wrapping for other elements.
Now if you want different layouts for desktop and tablet. You’ll need to adjust a couple of ways. There are 3 or 4 ways to do it. Alternatively, you can simply adjust each device’s view manually for the 100%.