Could you please help me with ways to complete this sentence?
Zu meinen besonderen Interessen (in meinem Studienfach) gehörten/ gehören vor allem …...
My dictionary tells me that "X zu Y gehört" can mean "Y owns X" or "X is a part of Y" or "X is a prerequisite to Y", but I'm not sure which meaning is used in the sentence above...
Etwas gehört zu etwas/jemandem (a)
(note the "zu", and look for a better dictionary if yours doesn't point out the difference) means something different than
Etwas gehört etwas/jemandem (b)
(b) is about ownership only.
(a) mainly means "x is part of y" (I) or "x is a prerequisite of y" (II)
In your specific example, (II) doesn't make a lot of sense (because subtopics can't be a prerequisite to interests), so it must be (I).
You would translate as something like
x, y, z were amongst my interests...
"X gehört zu Y" can also mean something like "X belongs to category Y" or "X is a member of group Y". For example,
Die Hunde gehören zu den Säugetieren.
Dogs belong to (the category of) the mammals.
or
Er gehört zu den Anfängern in seinem Tennisverein.
He is a part of (the group of) the beginners in his tennis club.
or
Sie gehört zu den größten in ihrer Klasse.
She is a part of (the group of) the tallest (students) in her class.
So,
Zu meinen besonderen Interessen (in meinem Studienfach) gehörten/ gehören vor allem...
means something along the lines of
Among my special interests (in my field of study) were / are especially...
