What can you do to protect the air? Can we say that by handing over waste paper, we protect the air?

Yes. By handing over waste paper, we save trees, which means we save air. Waste paper is recycled, as a result, the paper is reused. This prevents the cutting down of shit, which is known to be involved in the production of the oxygen we breathe.
In addition to handing over waste paper, we can plant more trees and other plants, protect existing ones, build fewer factories and stations, and not pollute water bodies that also have plants.