Hi Amany, it sounds like you've got a happy Epiphyllum on your hands
The way you describe the growth sounds right to me,
new "leaves" coming from the top and sides is not unusual.
You're right about not going oversized with a new pot,
in fact, my experience is that they bloom better if they are a bit root-bound.
Many Epis have a pendant growth habit, and yours may be that type.
It may, in time, make a great hanging basket
plant.
In the meanwhile, perhaps you can add a support stake,
and just gently tie or prop the
plant up
(try not to disturb the roots, they don't like that very much
).
You said that this is a new type of
plant for you,
there is some wonderful info at
this site if you'd like to learn more.