HOW TO GET RID OF UNNECESSARY TRIMS?

I am learning to digitize using Hatch lessons. I have upgraded to Hatch 3, but I wanted to finish the practice digitizing that I started under Hatch 2. It was the hand mixer. The instructor states this practice design should only have 1 trim in total! I already have 13 and don't know how I got them. Some of them don't make sense so I think they may be something that I accidently click the screen or something.

Since I am new to digitizing, I don't want to just start deleting trims not understanding what I should be looking for to know what to delete and what to leave. Is there a lesson about removing trims that aren't needed? How do I get rid of them and where should I look to find that kind of information?