there are 3 main sections to this-
the expository section is from m.1-24. The melodic line repeated in the first section
the second section (B), plays around with the dominant key (f maj). This section is also very piano and legato compared to the A section. The B section goes until measure33. Then the A section returns wit the same structural phenomena as before. I noticed a slight Pac in meas. 36 (back in Bb) . This whole section repeats again. The third section begins very piano and sotto voce, and is in gb major (it's easy to tell by looking at the bass line) but is very unstable in the right hand. It leads right back into the expository A section at measure 53 and ends on a very stable PAC in Bb on both the first repeat and the final end.