Is these sentences are correct.

Question

Even though we have discovered thousands of dinosaur fossils, we still don’t know much about these creatures.
While they dominated the earth longer than humans have, they suddenly died out for unexplained reasons.

Answer 1

Again ... we need to clarify your instructions.

Answer 2

make that two sentences
COMBINE THE SIMPLE SENTENCES INTO COMPOUND AND COMPLEX ONES

Answer 3

Yes, you're right.