I'm not a Muslim, so I have no obligation to observe the fast, but since I live in the same apartment, it's important to be considerate of those customs.
Literal
I [topic-は] Muslim is-not [because-ので] fast [object-を] observe obligation [topic-は] not-exist-[explanatory-のだ][but-が], same apartment [at-で] live [as-long-as-以上], such customs [to-に] be-considerate [thing-こと] [topic-は] important [thing-こと] is-[copula-だ].
A thoughtful cross-cultural observation. ~以上 ('as long as, since, given that') is a conjunctive meaning 'given that X is the case.' 断食 ('fasting, fast') is the standard term for religious fasting, central to Ramadan. ムスリム is the loanword for 'Muslim.' 配慮 ('consideration, thoughtfulness') expresses active thoughtfulness for someone else's situation. 慣習 ('custom, convention, practice').