I don't know when you need "a" before "part" and when you don't.

Native speaker’s answer
Rebecca
There's no real difference between the two! In general situations, you could use "a part" or "part." Even here, it would mean the same thing and sound natural if you were to say "part" instead of "a part." The only slight difference is that "a part" emphasizes a singular part of a whole, and "part" means to be involved in or in something. Although "part" can also mean "section," and in this situation, you can't use "a part." Ex: She's part of the team. = She's a part of the team. Ex: This part of the cake is going to be iced. => section