Xjyuk

I am a student and I usually have to sit on my study desk each day including weekdays and weekends for about 13 hours or more I have a pretty hectic schedule and I sometimes suffer from back pain (lower back and shoulders) which can we help severe and also affect my studies.

I am looking for any piece of advice that you can offer me to we ease this problem of mine.

Anything like various exercises, postures, devices, things to take care about before it gets too late or something that I might ease the pain.

Please please help.

Sorry for my english. I am a programmer by myself and often spend about 10-13 hours/d in the chair and had the similar problems.
My solution - exercise 20 mins full body everyday, but do more 'active' physical activities on your back and legs. I mean - no bench exercises - do a lot of reps of berpee, deadlift, upper push ups with lightweight dumbells, pull ups. Do a lot of core work - bycicle, plank - everything, that makes your body 'curl up'. Don't rest more than 30 secs. You can take a look on crossfit exercies. Be more active. Go for a 15 min walk between your study activities.
Everything of above mentioned will take no more than 30 mins for a day, but it will help you to get rid of your back pain.

Check it out
https://wodtimecalculator.com/blog/201-crossfit-workouts-can-home-pdf/

First you need to realise that sitting all the time is not just bad for your back, but also bad for your learning. Break the learning into chunks of about 20min. Use the breaks for exercise.

This should actually help you with learning, so don't even get the idea that you have to add the "lost time" at the end.

Depending on your current fitness level a range of exercises might fit but I'm going to assume that you are rather unfit given the schedule you describe.

I'd start with getting one of these big exercise balls.

Balance on it on your knees and hands.
If you can hold that stable stretch one hand or foot out at a time and hold for 10s at a time
If you can do that stretch out a foot and the diagonal opposed hand and hold again.

If you can do that get a body weight fitness app that allows to do and track single exercises.
I like Freeletics but there are tons out there.
The free version of Freeletics should be fine so this doesn't have to cost money assuming you have a smart phone.
Do one exercise each break and you'll see a tremendous change including less back problems.

Additonaly consider a standing table.
And an instable chair which forces you to balance your body yourself instead of slouching in a comfy chair.

Finally possibly the hardest part:
Stop studying 13 hours a day.
A brain needs rest to learn.
Limit yourself to 8h a day weekends off.
Or you will hate yourself in 1 or 2 decades.

This article from Business Insider talks about a study that concluded that 52 minutes of work followed by a 17 minute break was the work cadence that the participants' best employees used.

You can use whatever cadence you like, but the core principle -- from both a physical and mental fitness perspective -- is to get up and move every hour. If that's a 15 minute walk around the block, great! If it's 30 seconds of jumping jacks, it'll do. But whatever you do, take an hourly break and move your body around during that break!

Yoga's cat pose is perfect for this. 2 minutes of it before going to sleep. And then 2 minutes of extended cat's pose with stretching opposing arm and leg.

Your pain will go away, and you may forget doing the poses - and the pain will remind you to do them again.

Source: personal experience, for many years now.

You want a standing desk. Starting at about $150.

You should aim to put those sitting hours below 8, not for your back but for general health, and it (probably) won't make your back pain worse.