Your mind has stopped working. Now write first and clean it up later. Stop working, take a break. Try to relive your scenes and start in the middle. Start and stop scenes at better positions. Recapture your thrill of writing.
Hard, heavy, difficult writing. Go back where the writing made you feel good; you may have a deadlock and feel a character has to go.
An ending that makes or breaks a story, leaves a lasting resonance. They need a climatic scene, great music, a full range of emotion, heightened conflict, and an unforgettable ending.