我主修的是日語，因為我想要多學一個外語。除了主修之外，還有選修市場營銷

我主修的是日語，因為我想要多學一個外語。除了主修之外，還有選修市場營銷課程。

結果 (英文) 1:

My major is Japanese, because I want to learn one more foreign language. In addition to majors, there are elective marketing courses.

結果 (英文) 2:

My major is Japanese, because I want to learn one more foreign language. In addition to majoring in marketing, there are also elective stake courses.

結果 (英文) 3:

My major is Japanese, because I want to learn a foreign language. In addition to major, there are also elective courses in marketing.