They cut a lot. Firstly, they cut Part 1 of the sequel and instantly started with Part 2. Part 1 was a Shonen and looked completely different. Then they skipped many chapters and only included one arc. But that arc spans across many volumes. Here is a list of chapters they adopted:
V4: 1-6
V5: 7-13
V7: 14-15
V8: 16-17
V10: 18-24
V11: 25-31
V12: 32-37
The series has 20 volumes I think. And even in some of these volumes, they didn't adapt every chapter. I haven't read the series, so I don't know how self-contained the Viz release is, but I always prefer it when the order is faithful to the original