First of all, stay calm. It'll be alright! Just take a deep breath, it's no big deal.
Here's how to open a lock:
first, turn it to the right a couple of times.
then, turn it to the right to your first number, which is 24.
then turn it left and pass 26 once before going to it again.
finally, turn it to 16 once and pull down on the lock to open.
(don't worry, it took me a whole day to figure out how to open my lock for the first time, but after I learned, I was able to do it in like five seconds.)
I'm not sure how long it would take you to do your homework because it depends on your school and teachers and how much homework load they give.
A couple hours should be good, maybe more if it's difficult.
Your first year might be a little hard, but it's only because you're adapting to having more responsibility and homework. Just work hard and do your best, and don't forget to be nice and make good friends! You'll help each other out through the year. :)