Great effort! Your sentences are almost perfect. Here is a corrected version and a short, simple explanation.
Corrected sentences:
There are many wild cats. The big ones are lions, tigers, leopards, and jaguars.
Why this is correct:
- "There are many wild cats." is a complete sentence. It is correct as you wrote it.
- In the list "lions, tigers, leopards, and jaguars," we put commas between the animals. The comma before "and" (called the Oxford comma) is optional but it helps make the list clear.
- The animal names are common nouns, so they stay lowercase (lions, not Lions).
- If you want to ask someone to check your grammar, write: "Please check my grammar." or "Check the grammar, please."
Nice job! Keep writing short, clear sentences like these.