Technical Interview for a Company that uses Proprietary Software

Hi there!

Recently I had an HR prescreening for a software development position. The HR person was impressed and set up a time on the spot to go forward and do a more technical interview with the actual development team.

I’m trying to think about how to prepare myself for the interview, but HR mentioned a lot of their software is “proprietary” and will take anybody time to get used to. I know that the company primarily uses C# (which I am the most familiar and comfortable in) alongside some SQL, python, React.js and a bit of VBA. Anything that would be good to brush up on/practice for this? Thanks