I recognise very well the problem you are facing. It was a huge problem for me when I began reading philosophy for a degree. I can only offer suggestions that may help, not a magic keep. To illustrate my parallel experience, it took me six weeks to read Richard Robinson's 'Plato's Earlier Dialectic'. I calculated that at that rate I would not cover more than a fraction of the required reading.
I adopted two strategies :
1 Faced by a long text I would read it through quickly, not taking notes but just getting a sense of the topics covered. Even from this light reading I could tell that not everything in the book was equally important. The second reading, the close reading, was much easier because I knew what was coming. Also I knew the text did not need to be read throughout with equal minuteness. When I first, quick-read the 'Republic', for instance, it was obvious that on a philosophy course I was not going to face questions on the early education of the guardians or, fascinating though it is, the Myth of Er. It was clear that the central books, IV-VII, were where the tough philosophical problems were located.
[I now read the 'Republic', all parts of it, for its endless suggestiveness but I am now a retired lecturer, not a desperate student !]
2 Books are terribly time-consuming. Some you have to familiarise yourself with but not all. I quickly discovered that articles were a lifeline. Two or three, or three to five, good articles will present you with a variety of viewpoints, all you need, and if of high quality they will give you sharply focused material that you can absorb and apply to impressive effect. Most books contain some or a lot of material that you don't need. This is seldom so with an article; and when it is so, the brevity of the article allows you quickly to spot it.
3 Make use of journal articles, many of which are online in most libraries. Also subscribe to a magazine or two : 'Philosophy Now' or 'The Philosophers' Magazine' but also a journal such as 'Philosophy' (issued by the Royal Institute of Philosophy) of higher intellectual stamp.
That's all I can offer, I'm afraid. These methods worked for me. They could well help you as well. All best wishes to an aspirant philosopher !