I have a long monologue. What's the best way to learn it?

Break it into smaller chunks:

1. Tap the long line → three dots ⋯ → Edit Line.
2. Select and copy the text, delete the latter half → Save.
3. Tap three dots ⋯ → Add Line Below.
4. Paste the text → remove the parts already in the previous line → Save.
5. Repeat until you've split it into manageable sections, then use Stack Lines to rehearse your way through section by section within the monologue.