Map right shift key to behave like top arrow guys I'm a software developer and I use arrows keys a lot. 
As long as Apple changed their keyboard layout it is so hard to use the new arrows setup. It' just drives me crazy every time when I try to go line up, or line down in my code editor. 

Is there a way to map RIGHT SHIFT key to behave like a top ARROW ?
And map TOP ARROW key to behave like DOWN ARROW. 

It would be a great solution for me. Thank you for your help. 
I've been trying to achieve this by Ukulele app, but I don't understand this app or I'm doing something wrong.
I've not heard of Ukulele and it wasn't in the top ten search results on DuckDuckGo.  So, allow me to recommend another third-party piece of software, which is open-source, well-established, powerful, reasonably intuitive, and widely known and popular in its use with developers and "power users".

Karabiner Elements is stable in and updated for macOS Catalina. 

Most keyboard mappings will be achieved using the GUI in a pretty straight-forward interface.  For complex mappings, there's a configuration file you can edit which uses JSON (Karabiner .json Reference Manual).

Yours are classified as simple modifications, e.g. ⇧ᴿ ⥱ ↑, so can be created straight in the GUI. Here's a screenshot series that shows how intuitive it is.