You're doing the right thing by having regular breaks as that will allow you to refresh your mind, which will in turn allow you to become more productive as you get back to studying. The problem I'm seeing here is that you're probably allocating too much time towards your breaks. 30 minutes for a break seems like a bit too much time, but to answer your questions directly:
a) You'll have to put in the effort and implement all the necessary strategies in order to become able to study for longer periods.
Effort in this case means that you must concentrate on your studies during all of the time period in which you are studying. Absolute concentration on your work implies placing 100% of your focus on studying, which enables you to be in the appropriate mindset that will make you capable of studying for longer periods of time. This is not an easy process, and you should not expect this to work from the first time. Being able to fully dedicate your efforts towards studying/preparations/revision takes time and is a type of mentality you will need to get used to in order to achieve this goal. You also need to recognise that while it is definitely possible to study for longer periods of time, there will eventually be limits that you cannot exceed, meaning breaks will always be needed at some point. The
necessary strategies in this case include:
- Getting rid of any distractions, particularly while you're studying. Those include any devices you don't use for study like your phone, or any other objects/factors that might distract you while studying. This ensures your focus is on your studies, not on anything irrelevant/may cause you to waste time.
- Lower the time you allocate towards your breaks. As I mentioned, I feel that you're currently allocating too much time towards your breaks. While the point of breaks is to refresh your mind so you can get back to studying and being productive while doing so, breaks that go for too long may result in your brain leaving its "study mode" and entering a more "lazy" or "non-study" mode. This is something you should definitely avoid because your brain will not work as intended as you get back to studying, i.e. you are less likely to be as productive as you want to be, which ultimately obstructs your ability to study for longer periods of time. This is because your brain will either partially lose its focus or completely lose its focus as you get back to studying. In terms of how much time you should allocate towards your breaks, I believe your breaks should approximately go for 15-20 minutes maximum.
b) As I mentioned, reducing the time you allocate towards your breaks will allow your brain to remain in its "study mode", meaning you will be able to maintain the same 100% focus mentality you had prior to having your break as you get back to studying, while at the same time still being able to effectively refresh your mind, allowing you to potentially study for longer periods of time. Another thing that you can do to set strict limits on your breaks is to limit the use of any objects that may cause you to get distracted, including the examples mentioned above, and, if possible, avoiding their use altogether. For example, a common problem with using your phone to check your messages and/or social media as well as watching YouTube/playing a short round of a video game etc. is that this can go beyond your break time without you noticing, leading to the 3-4 hours you're currently wasting. Not only will avoiding of all of those distractions give you all that lost time back, but it will also ensure your studies are more effective and efficient overall, as explained in a).
I hope this helps!