Question

How could you use the word main in a sentence but in an adjective way pls help

Answer 1

My car is my main way of transportation.

Answer 2

An adjective is a describer.  Main means primary, so the "most typical"

The main reason he left the party was because he was tired

Even though there may have been other reasons to leave the party, the word main distinguishes that the fact he was tired was the biggest reason he left.

Hope this helps!