Hi, there's a pretty common bug that makes the game run slower than it should (around 30-45fps rather than 60fps). It sounds like your game is now running at the intended speed. Are you on Windows 10?
Since you're still having that problem, could you help me test a possible fix?
https://github.com/omicronrex/gms_scheduler_fix/releases/tag/v1.0
Someone has made a .dll that might fix the problem for all games that use the same engine. Just download DGBHELP.dll and place it in the First Cut folder. If I can confirm that this .dll fixes the problem then I will release an update that includes it.
The bug is what causes the game to run slowly. It should be running at a solid 60 frames per second, and it will play in slow motion if it doesn't. From the sounds of things your game is running at a lower FPS than it should. The gameplay gifs on this page should give an idea of how fast the game is meant to look.