I graduated from Mechanical Engineering and now working in engineering field.
Not an easy degree to take (although I didn't graduate in Canada I guess everywhere is pretty much the same), individual/team projects weights about 50%.
Good at maths is only one thing, more importantly is your problem-solving, communication and team skill.
修政治,国际关系,哲学这类 - You don't need these crap in China to be a civil servant, anyone could be a civil servant in China, all you need is relation
学经济,随大众 - Don't just follow, you live at your own destiny, but not base on what happens around you
想修工程,可是理科不好,就真的不要修了,对吧 - Have you ever tried before you said this?