How to write a personnel management system?

Question

Work organization

The task is to write a system for accounting and personnel management, at first I decided that I would write on ASP.NET MVC 5, everything went well, they started using it, but as soon as reports or minor changes in the system started, it immediately became clear that I had chosen something wrong.
What do you recommend, what systems to use? I looked towards the workflow foundation, I don’t know if it can be used for these purposes. I looked at the ready-made solutions on the git, but they do not fit.
By the way, it would be desirable in C #, you can also use javascript, nodejs, or, well, PHP.

Answer 1

rest api + angular\react
if there is rest api, adding mobile applications is not a problem

Answer 2

Oracle