How to maintain solve speed

How to maintain solve speed ?

lets think real situation.

   1⃣ when paper on table are too many,
       is it good environment to study ?
   2⃣ when your textbook contains not related info,
       is it good textbook to study ?
   3⃣ when we does physics homework,
       if physics text have over 10000 pages,
       is it good text to search theory ?
   4⃣ lets think situation,
       your friend had study 10 hour in 1 day before.
    if your friend study time become half,
       is it good to maintain solve speed ?
   5⃣ lets think situation, 
       you have given homework, 
       about too difficult problem.
       is it good to maintain motivation ?
   6⃣ lets think situation,
       your text full with difficult theory
       that you never seen before
       is it really good text ?

   writers recommendations :

   1⃣ to clean up table & prepair necessary text may good practice
   2⃣ to write only necessary info in textbook may good practice
   3⃣ text, may better, if easy to search essentials
   4⃣ if solve speed is same,
       solve time × solve speed ～= solve quantity
       then maintain solve time, may better
   5⃣ solve from solveable problem, better
       (  too difficult problem, means nothing  )
   6⃣ textbook should readable, to who study first time

   there are element of solve speed
   ⑴ availability of information      ( 1⃣2⃣3⃣ )
   ⑵ investment of time to solve  ( 4⃣ )
   ⑶ problem have order to solve ( 5⃣ )
   ⑷ readability of information      ( 6⃣ )

   => we can increase solve speed,
       if we care ⑴⑵⑶⑷