One of the meanings of "since" is very similar to the meaning of "because." However, there are some differences in the ways the two words are used, which are very hard to explain to a non-native speaker. So you should probably use "because" until you become familiar with the differences.

I reckoned you sure were Chinese immediately as I saw the question. I was taught some bs as well at school, "since, because, as, for, due to, by reason that etc". I think the teachers were just messing up with them, making no sense. Sometimes those two are indeed interchangable. Just follow your language "intuition", when you feel like an "由于，既然", use a "since" there, when you feel like an "因为", choose a "because". Yeah, that simple.

Since Preposition 1.From that time "happy since getting married" Conjuction 1.For the reason that; on account of "Since it's snowy, let's go skiing" Adverb 1.In the past 2. Happening at a time subsequent to a reference time Becuase 1.For the reason that; on account of I couldn't come because I was ill" cowboy...