Not sure, if my answers make it still more confusing but I`ll give it a try:
The core frame of an enneagram type consists of the passion, the motivation, the fixation and a few more things and it expresses itself in a specific pattern with certain variations. There are a few people who know of their passion right from the start, but most don`t. As you often can`t detect the basic passion and motivation especially if you want to type other people, following the type pattern is a good idea. Though it`s a bit tricky. If you describe it in a plain way which everybody can understand it will get unavoidably superficial and if you give hints and clues often nobody who doesn`t already know the type patterns will understand you.
Enneagram is about motivations but people are trying to type themselves or others according to superficial traits.
Sometimes people get stuck to superficial traits and sometimes superficial traits will get the intuition busy and you will see the type clearly.
Then you start to question yourself: is it that I do not see myself clearly, or that I do not understand the Type, or that people do not understand me?
Often it`s a mix of all three. After knowing the enneagram for ten years a friend of mine realized that she`s a Six, and not a Four as she believed. Surely she knew about her fear but was deluded as to the extent fear ruled her life. She`s no exception. I know a few others who retyped themselves after a few years. Even if you know your type right from the beginning there`s always the possibility that a time will come when you are ready to see right through one of your illusions. Self-awareness is a process which unfolds over the years.
What if a person has more than one motivation or has a motivation that is none of the 9 types?
You should start to improve the enneagram.

No, seriously, the enneagram is a rich and deep personality system. If you think you have more than one motivation it`s far more likely there`s still a lot more to see.
It is very hard to see the real people as there are so many mistyped, and most people around me are either not interested in Enneagram or started an argument whenever touching the topic of Enneagram.
If they start an argument that`s wonderful. You can see a type most clearly if the person is a bit stressed and outside of his or her comfort zone. Reactions tell far more than fine words.
Even if people mistype themselves you can start from there and learn through trial and error.
So would you say this girl was born to be good at maths and logic or trained to be logical after all those years?
No, I would ask this girl why she studied all these years if she hated it that much. Also why did she became one of ten girls in the mathematic class if she wanted to be different?
I do not understand the question. Could you please rephrase it?
You wrote that you were looking for yourself. What will be if that happens and you finally find yourself? A what-will-be-question. Can you imagine yourself that way?