Yes, "some knowledge" works.
Student or Learner
Some knowledge gained from school is still fresh in their mind, therefore they do not need too much time to revise.
Does the bold part sound natural to you?
Please, correct all my mistakes. I should know English perfectly and if you show me my mistakes I will achieve my dream a little bit faster. A lot of thanks.
Not a teacher nor a native speaker.
I'd use 'minds', unless they have a collective mind.