Nice work! Here are corrected sentences and a short, easy explanation you can understand.
- Corrected sentence 1: The Arctic fox molts — it sheds and regrows its fur — so it looks white in winter and brown in summer.
- Corrected sentence 2: In winter the Arctic fox is white, and in summer it is brown.
- Corrected sentence 3: The fox molts when its fur changes. (You can also say: The fox goes through a molt when its fur changes.)
Short explanation:
- Use the verb "molts" (or "moults" in British English) for one fox: "The fox molts."
- Use the simple present tense for facts that are always true: "It looks white in winter."
- Avoid saying the same thing twice. Sentence 2 was a little like sentence 1, so we made it shorter and clearer.
If you want, I can make a single short paragraph using these ideas for a school report.