Update Old Project (Software to run medical office)

I have some very old software that was developed years ago to manage a medical provider's office. Specifically, the software focuses on the ability of providers to generate encounter notes.

I have included the code with the project as well as illustrative videos that show how the software should function. Keep in mind we'll need to make changes here and there in the functionality.

I would first be interested in hearing your approach to this project. What's the best language to develop in and why? How long would this take? (Seems like the old project took about 8 weeks). Could the project be developed in a flexible manner so that future modifications could be made easily? Would it be easy to allow the software to interface with other entities? Should this be a web application or desktop application? What would be your time and cost projections.

Thanks for your interest.