So recently I started my internship and the first thing I was told is that I probably won't meet with users (HR managers) nor do I get their feedback at least in the early stages of the design. I am designing various dashboard features one by one. As for understanding their needs and goals I created personas from LinkedIn job notices and reading couple of articles about what it means to be an HR manager. I am no UX pro, I just finished my first certificates from Interaction Design Foundation and been doing just couple of projects for my university. So I am turning to stack exchange for help.

How would you go about designing and testing without the real users?