Answer:
Sure, here are the completed sentences with the correct possessive pronouns:
1. All the paintings in the gallery were painted by me. They are **mine**.
2. I don't like my lunch. I like Neha's. I am eating **hers**.
3. Did you leave your umbrella here? Is this **yours**?
4. This is not our classroom. **Ours** is on the first floor.
5. After they came to our house, they invited us to **theirs**.
Feel free to ask if you have any more questions or need further assistance!
