Hey Prini!
Unfortunately, this question is pretty broad! In terms of how the assumptions are written, my natural go-to response would've been a sequence of dot points, summarising what you have decided was necessary for the model/task! Your teacher may demand more, but at first glance I can't see how that'd be a problem.
Whereas for what assumptions to write, I'd think about what could potentially invalidate my model! For example, the syllabus gives a sample task of
"a report that investigates motion sickness on a Ferris wheel using the up and down velocity and acceleration of the Ferris wheel car".
Some assumptions could be that everyone was in an adequately healthy state before the experiment (and hence the velocity and acceleration are the only significantly-contributing factors). Or it could be in how the velocity and/or acceleration were modelled, for example linear, quadratic, some weird function.
Don't know how helpful this is at all, but if it's not helpful please elaborate on your question more.
(Without revealing too much of your actual assessment task though, of course
)