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Well, congratulations on your admission.

I don't know for your school, but in my first year exams, 90 percent of the Exams were from Past Questions.

I hated attending lectures, the hall was always full, Always!
I got past Questions and old 'hand outs' from those in 2nd Year.
I hardly went for lectures, in fact there were courses I didn't attend a single lecture for the whole semester.

I didn't do bad in the exams , I passed all my papers, Thank God!

( Get past questions, compare and see if Repetition of Exam questions is done for Year 1 in your school too)

If you're not fully ready for those 'hard courses', meet your Course Adviser. Explain things to him/her.
If you want to move the course to 2nd year, while you prepare very well for it, fine... ( this is possible, but not easy. It is best to write and pass now than to defer it for a year, it will be more workload for you... But if you indeed can study and learn those calculations before the next session, then you're good to go)
It still depends on how things work in your school.

You can form reading groups with your course mates.
Remember, never judge anyone by physical appearance or by your own guess, if he is intelligent or not.

There is a guy, in my department, he looks so unserious in appearance, I mean, he has beards all around his face, unkempt hair, always joke around... But, this guy is a Guru. I mean, Real Guru when it comes to the course.
Never conclude on anyone's intelligence but mind the people you become friends with. University is a world on its own...

As your resumed late, holidays is fast approaching and rumor has it that universities are planning to go on Strike, so every school is rushing to Vacate before they embark on strike... There may be no time for you to go do side jobs. You have to totally concentrate on your studies.
Your 1st and 2nd Years of studies are the very most important and determine what grade you graduate with.

In all, do your best. If it's sleep, cut down the number of hours you sleep.
Any thing that doesn't add to your studies, put it on a hold ( As you did with Football)

I wish you all the best man!