Both "The whole of" and "All of" feel unnatural to me. I'd go with Michael's suggestion of "The entire first part."

That's just it, both sound awkward to me. The first could be wordsmithed as "the whole first part..." and that sounds a little better. In my opinion, the "whole of a fraction" structure is the thing that's problematic because they're contradicting ideas.

Neither is really wrong. "The whole of the first part" reads a little better in your context, though you are allowed to cut this down to "the whole first part" without breaking any rules. This is more of a style choice than a grammatical necessity. "All of the first part" is also OK, but it has less impact. That's perhaps what Torusan was hinting at: "The entire first part" ("the entirety of the first part") also puts a little more weight on the message - which is a significant one for your point.

Thank you very much But between the whole first part and the whole of the first part, which one is right? What about "all of the first part"?

Instead of "whole", it's better to use "entire" in this context: "The first part..." or "The entire first part..."