in lesson 11 this was stated:

"Many" = "Some"

You could think of "many" as being equivalent to "some." Let me be clear: this is false. We already established that "many" has a higher minimum threshold than "some." But, it's a useful falsehood because I've never seen the LSAT penalize this conflation.

but in this lesson "many" implies "some", can someone please explain..

If one is a Jedi, then one uses the Force. Luke is a Jedi. Therefore, Luke uses the Force.

being a Jedi guarantees you use the force, but using the force does not guarantee you're a Jedi?

For number 2, when I saw the answer (no argument present ), I realized afterwards that I forced myself to think that there was a conclusion instead of a set of facts due to being uncertain.