I spend most of my day studing, i sometimes have to sleep for 3 or 4 hours. I have to do this because i have a lot of work to do (even if that work is done in time). So my question is, how should i schedule my sleep habit, taking in considiration that i have to be awake by 6:30am, I have lectures usually to 5pm, having my meals, doing my work when i get home, walking everyday to Uni and back for like 1 houre and 30 min, and last, having a at least 7 hour sleep?

could you be able to do your school works earlier when you are still in school, maybe between the lessons or on the lunch break
maybe you could transfer some of your work to your phone so you could do something on your time when walking to uni
maybe ask your teacher to give you more time to return your school work
but most importantly split up your work in parts so it will be easier to complete them
take care of yourself and your health because it will be a burn-out in the end if you don't take a break in between
hope this helped you even a little bit

Try to schedule when you want to do something. And if you are a lot of time on your phone particularly on 1 app then try using YourHour. And try to relax becose you got this!