Hi Kati –
First, thank you for the encouragement! It is wonderful to hear that your homeschooling experience was so positive and prepared you for college well.
Secondly, learning to narrate is such a good exercise for your mental clarity and composition skills. I wouldn’t worry too much about the ‘length’ of your narrations – I would concern myself with the amount of detail you are able to provide.
The main point of narration (as I understand it) is to establish a clear, coherent train of thought complete with detail and opinion. So, if I were you, I would start with short passages and once you have mastered retelling them in a detailed way, move on to longer and longer passages.
Hope that helps a little! Blessings!