I am unable to update my iOS because my internal storage is full. I am unable to delete or update apps. What do I do?

If your storage is full, you'll need to remove things you don't need or use, such as Apps, Music, Photos, Files, Videos, Messages, Email, etc.

If you are unable to delete apps, go to Settings > Screen Time > Content & Privacy Restrictions > iTunes & App Store Purchases > Is Deleting Apps marked Allow?

You can if you want, update your phone using your home computer with iTunes. But you really need to reduce the memory on your phone as phones which are out of storage, don't run optimally to begin with.