Complex sentence: Human exists, material exists, air exists (and almost up to the end of our life we already have used our lungs for 500 billion times), we are not able to see air but we intensively need it.
Split into simpler sentences: Human exists, material exists, air exists (and almost up to the end of our life we already have used our lungs for 500 billion times). However, we are not able to see air but we intensively need it.