What software are you using?
Chevy_man said it already, Davinci Resolve. It's a fully featured video editing program for free, kinda like Fusion 360 is for CAD, but even less restrictions. I also use Audacity for recording voice overs and any extra audio editing I need to do, and OBS if I need to record my screen.
Resolve takes some time to learn, focus on the Edit tab, don't worry too much about Fusion or Fairlight, the Color stuff can be useful to do corrections if need be (color balance, brightening, etc.), and of course Deliver to actually output your video. Edit is easy enough to slice/dice pretty much everything, layering your media, and basic effects. If it runs slow, make sure you do optimized media HQ (not HQX) at half resolution, and should run fine on most computers.