I tried using obs but every time i watch the video back the video is just black. Does anyone have any suggestions?

you can use OBS and set the capture to the sexyhiking executable under game capture once you have open the game but this will create a large black void around the game footage due to sexy hiking running at a low resolution that you will have to crop out.

I managed to take a recording of a good attempt but I dont know how to crop the video.

i use software like Davinci Resolve but https://ezgif.com/crop-video works just fine as well. Just know that using this will degrade the quality of the video slightly.

Free tools like Free Video Cropper https://www.easymakevideo.com/freecropvideo.html are fine if you just cut the Video. If you're looking for something more comprehensive tool, Easy Video Maker is also an easy but powerful all-in-one video recording and editing software.