i'm also a beginner diver, i've been training solo on and off for the past 3 years
i did much reading too
i recommend you read the diving manuals by AIDA and apnea international as a foundation for any further training
for training in the pool, i recommend you find a pool with a present safety guard who is actually paying attention
but what i found works for me, is to do dry static and dynamic training outside of the pool
and use the valuable pool time not to push my limits, but to train technic
its a valuable advice, one, you dont have much time in the pool compared to dry time, so any apnea training in the pool is a waste of time and safety risk
i recommend you do dry statics and dry dyamnics (walking apnea, jogging apnea, anything that makes you confortable)
and in the swimming pool, never push your limits, train swimming technic all the time, i only need to swim 20meters
and i use that distance to measure the number of strokes, with plenty of rest time
so i'm never at risk of hypoxia or hypercapnia
i dont know how many times i will stress it out, no pushing limits in the pool, and its a waste of time anyway, you can do apnea training in dry land
and you have all the time you can get
what you cant train in dry land, is actual underwater swimming, and that's what you should be doing in the pool
currently my dry static is 6min and my DNF is 50m and DYN is 75m, (from last year, this year i coudnt go to the pool since last summer)
i recommend you do swimming drills with your legs only and hand only like reducing stroke numbers to cross the pool, this is your benchmark
then combine them and also reduce that, also your streamline by doing wallpushs and measure distance till you stop
optimizing your buyoancy control and streamlining will make you gain lot of efficiency in water
while training outside the pool your dry static and dynamic will be your general progress
when the time comes to rest your progress by doing actual DNF/DYN max, find a coach or buddy