Ithas a lot of pockets. I use them all the time, and I made some of my ownmodifications.

这是在说一件衣服有不少口袋,但黑体部分我理解不了,请问:

1.some是代词然后of介词短语修饰some吗?若是如此意思就变成了“我一个人做的改装中的一些”,这逻辑不通呀。

2.为何不是I made some modifications of my own呢? 

语义上 some of myown modifications = some modifications of my own。像 Some of my friends = some friends of mine. 但侧重点有所不同。句末是信息中心。前者突出modifications,后者突出my own.