What do i do when competing in chess competitions with a low ELO??

I’m 15 years old and I won the chess competition in our school and now my school wants to make me compete against other schools. The problem is that I’m not good at chess…I have no idea how to improve, the competition is in 7 days and I’m really nervous. I don’t know alot of openings and I suck at creating strategies and tactics. Should i get a chess teacher? Watch youtube? Read chess books? Play chess with my classmates? Please help me! thank you