There are a lot of choices. It probably all depends on your skill level. Also, you should take in mind that there are some soft that is only available just to mac os or windows. I would suggest using Avidemux or Openshot because they are pretty simple. Take a look at this list, and maybe you'll find something else.
Editing videos for YouTube doesn't need much professional and complicated editing software. You can try some free video editors. This review is detailed and includes the test environment and factors considered during the test. You can check whether they are fit your specific needs before installing an editor. Top 6 Free Video Editing Software 2020