Great job! Here are corrected versions of your sentences and short, simple explanations.
Corrected sentences
1. I’m Strelka. Together with Belka, I was one of the first dogs to orbit the Earth.
2. Fantastic! The Sun is a giant star that looks like a fiery ball. Without it, our planet would freeze.
Why these changes?
- Sentence 1: I changed it to "I was one of the first dogs to orbit the Earth" because Strelka is speaking about herself. If you want to keep "we," you could say: "Together with Belka, we were among the first dogs to orbit the Earth." Both are correct; the first is just a little clearer.
- Sentence 2: I used "would freeze" instead of "will freeze." We use "would" for things that would happen if something else were not true (this is a hypothetical idea). The rest of the sentence is fine and easy to understand.
Well done — your sentences are great! Keep writing and asking questions.