"Prelude 2 in C Minor" is a piece written originally for keyboard, but is transcribed for two six-string guitars. Because of the tempo changes and the endurance needed to get through this piece, it is probably the most difficult one in my book, "Advanced Classical Studies for Modern Electric Guitar", to perform.
PDF - Download the Notation
First, play it all the way through without stopping. Try to get through it five times. Second, Look at the whole piece. Third, work on the sections one at a time. I have notated the upper line at pitch and the lower line one octave higher and in treble clef.
See that it is divided into three main sections. The first section extends through measure 24. I'll call this section 1. Measures 25, 26, and 27 break up the sections. I'll call this the arpeggio part. The next section begins in measure 28 and extends through measure 33, I'll call this the Presto. Measure 34 is a kind of solo cadenza which bridges the Presto to the final section. I'll call measure 34 the Adagio part. I'll call the final section the codetta.
Now that you have looked at this and played through it, you are ready to begin working on the individual sections. Pay attention to how it sounds. You may need to spend a lot of time on a particular measure to get it to sound right. Just as you approached the whole piece, you can approach each section by first playing it through and then playing groups of measures. This strategy works.