Please help me correct my shory essay

The most important quality in a person is their respect for others. People usually get along much better, if they learn to respect one another. For example, I had a classmate in 3rd grade that peed on himself once in PE. When our teacher asked why his pant was wet, I told her I accidentally spilled water on him. After the incident, he and I became best buddies. Another reason why having respect for others is an important quality is it shows how mature you are. For instance, a friend of mine was paired up with someone he hated for a history project in middle school. I was sure they would get into a fight. To my surprise, they managed to work together as a team quite well. Whenever one of them needed a scissor, they asked very respectfully, "hey, can you pass that scissor to me, please." They eventually got an A for the project. By showing respect for others, you'll more likely to get a better response from them. One time I went to the school computer technician to get some ink cartridge for my English class. When I arrive, he was talking on the phone. I didn't want interrupt his conversation, so I waited for him to finish. After he was done, he immediately went and got the cartridges. He even apologized and told me if I needed more, I could come back. I think if I hadn't showed him respect when he was on the phone, he wouldn't been as nice to me. These are the reasons why respect for others is the most important quality in a person.

(I proofread it a couple of times, but didn't find any mistakes, but im pretty sure there are, especially in verb tense, grammar etc

please tell me what my mistakes are, thank you