How to give "tablet app" feel with rounded, 3D cells?

Hi guys!

I'm trying to format a drop down table so that I could show it to my clients on an tablet. Because of that I needed some formatting tips for giving it a proper "app" feel to it, either by changing colors, adding shadows, and making it intuitive in general.

Is there a way to give a rounded, 3D aspect to the cells, resembling an app?

If not, how could I use a format to individually group the input and results cells?

I've attached the file if somebody wants to help me with it (sorry it's in another language) and I've also translated the headings if it helps.

EDIT: I've just realized that data connections were enabled. I've now disabled them so that it's safer for you guys.

Mortgage financing.xlsx

Thank you very much!

Use a combination of big (right and down) and small (left and up) borders and /or black and gray border colors