Having studied all kinds of subjects for many years, we have formed our own plans on how to serve the world better and are well-prepared to put them into action.
I think the underlined part is not naturally written. Is "subject" collocated with "studied"? If not, what verb will do?What else could I write to describe "after we study English, math, history, economics and so on"?
Maths is a subject. History is a subject. Geography is a subject.
At secondary school, I studied nine subjects.
At sixth form college, I studied four subjects for the first year, but only three subjects in my second year.
Over the years, I have studied a lot of subjects. I have studied all kinds of subjects from maths to philosophy, history to business, English literature to lateral thinking.
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.