Same for out team; furthermore, it's our first released game as well!
We had some minor hackathon experience however (1-2 hackathons depending on the person), so coding under pressure of time was not a first for us, but I still think we've got a lot to learn about working in conditions like these ;)
The bigger hurdle for us was that we've never really done game design/programming and none of us had any real C# experience (with two out of four of us never having written a single line in C# !), which we had to use, writing in Monogame, so it was a constant learning experience with a lot of tutorial and documentation reading along the way.
Still, we've had a lot of fun, and I think we'll be looking forward to participating in some other jams over the year, in preparation for the next GMTK jam, of course! ;)
If you wanna check out our entry, have a look here: https://itch.io/jam/gmtk-2019/rate/462587