1. Open the Photos app.
2. Find and select the video you want to compress.
3. Tap "Edit" in the top right corner.
4. Tap the crop icon (a square with two arrows) at the bottom.
5. Choose "Aspect Ratio" and select a smaller ratio like 16:9 or 4:3.
6. Tap "Done" to save the changes.
7. If you need further compression, you can export the video using a lower resolution. To do this, tap the Share button and choose "Save Video". When prompted, select a lower resolution like 720p instead of Full HD.