Sentences

1. I needed to get to the first floor this morning, but wasn't able do so. Or

I had to get to the first floor this morning, but wasn't able to do so. Or

I wanted to get to the first floor this morning, but wasn't able to do so.

2. After three hours of running your body breaks down. Or

After three hours of running your body's broken down.

3. Scenario: I'm at the beach and suddenly the sun gets covered by clouds.

Can I say:

There's no sun! What happened? Or should it be:

The sun is gone, what happened?

Are all of these sentences useable?

Thanks!

Are all useable and grammatically correct? Thanks!