Also, start with just remembering and telling a section of teh story. The Mabinogion stories and the story of Talieson for example are all quite long and complex, and often include several stories stuck together, so just choose one section (e.g. the story of how Gwion Back becomes Taiesin, rather than the whole story of when he later becomes award). Or Pwyll’s encounter with Arawn and exchange of places in Annwfn, and ending on when he returns to his kingdom. Later lear the story of how he meets Rhiannon as a another story.