My movie editing program is HD movie maker pro, was in the Microsoft store. The store should be a windows app on your computer. I tried the free app, then bought the "pro" version, was about $10 one time fee. It was fairly easy for me to figure out, I am still discovering features that it has.
My GoPro is an 8 black. It has the linear function, called cinematic on the camera. I can sync it to be controlled by my Samsung phone, so I have remote control of start/stop and a larger screen to watch. Since the gopro 9 is out, there may be some good deals on the 8. I got an extra battery and remote charger, plus some extra chips.
Not being critical, just helpful, but mounting your camera, instead of holding it will give much better results. Then you can set-up scenes, get lighting right where you want it and run trains past the stationary camera. Extra mounts for tripod or stick-on bases are inexpensive, available from Amazon.
I am 70 today and it surprises me that I have been able to learn this modern technology, so don't underestimate yourself!