You can do it breh, you just need to believe in yourself.
I never studied in high school; I was getting blazed and fukking bytches instead. I even got thrown out of pre-college cause I used to do the same shyt. I woke up at 22 while working customer service on the phone and had a lot of downtime to wonder what the fukk I was doing with my life.
I read a book on python during work and studied math from the beginning. Now, ~4 years later, I got one year left on my math and comp sci degree and doing good.
Those examples of your friends doing calculus homework in 10 minutes, that's probably not because they're geniuses; they've probably been studying math consistently since they were younger, probably had parents all up in their shyt(good parents).
For real, there's such a thing as prodigies/geniuses(von neuman, gauss, euler,etc.) but few are cut from that cloth: a guy like von neuman is probably less than once in a century. Most people who are successful in life have achieved it through hard work and persistence.
Anyways, before I took this shyt serious as an adult, I didn't know how to derive the quadratic equation and still thought mathematics was just about memorizing things, and now I know all kinds of shyt from calculus to graph theory. It's hard to see the bigger picture as a beginner but try and google things like axioms, propositions, theorems, etc. and get familiar with how mathematics works.
Most of the textbooks schools use are bullshyt that hardly explain; they usually just state formula after formula with no proofs and hardly any intuitive explanations. They basically train you to be a computer and just use algorithms without really knowing what's happening, but if approached the right way, it's infinitely more rewarding than any video game could ever be.
If you're serious about learning, go
arithmetic -> algebra -> plane/analytical geometry -> trigonometry -> linear algebra/calculus -> analysis/whatever
Anyways, here's some good books to get you started.
Euler - Elements of algebra
https://archive.org/details/elementsalgebra00lagrgoog
Old book by a master. The language might be dated, but this is a very lucid presentation of algebra. The difficulty is probably a bit all over the place though so skimming over parts is no problem.
Basic mathematics - Serge Lang
http://libgen.org/book/index.php?md5=3dea10fd9a6a244f53708f90cd06929e
If you were to read only one book, this would probably be the best choice, it's basically all of high school mathematics.
Kiselev's Geometry Book I. Planimetry
http://libgen.org/book/index.php?md5=1702109368F65A67A6691C56616D823C
great geometry book, soviet era math books are the best because there were very advanced dudes making books on elementary subjects with a very intuitive feel.
Plane And Spherical Trigonometry
https://archive.org/details/planeandspherica029145mbp
great trigonometry book, don't bother with spherical trigonometry cause no one uses that shyt anymore (sailors used too probably like 600-700 years ago or whatever)
The subjects above are the basic tools needed for the next subjects so you need to understand them well before going further, so spend time going through these books. You don't have to go through them one after the other or even completely, but at least be aware of what you don't know or cannot do.
Differential and Integral Calculus - Piskunov
http://libgen.org/book/index.php?md5=3b4ea91bcc482321628862a84c3c5e95
One of the best calculus books out there.
Linear algebra and its applications - Strang
http://libgen.org/book/index.php?md5=AB808E56250882EFDE72BC65F5CA32BF
You can look at this guy's lectures from MIT on youtube too. Videos are great when you just start learning because good teachers are extremely explicit and give intuitive explanations.
Understanding Analysis - Abbott
http://libgen.org/book/index.php?md5=42fdd00d77cbe90a9e3f22ba511e5324
If you can read most of these and absorb the information, you're basically level 2 in mathematics and it starts to get more interesting.
For comp sci, you should probably start with python(many would say ruby). The language is very clear with little overhead(learning to compile stuff, declaring variables{static typing} and all that noise), just search on amazon for a book that has a good rating, then read a book on data structures and algorithms, the classic text is
Introduction to Algorithms - Cormen
http://libgen.org/book/index.php?md5=E07DD7CDAFED5967F6B3EFEC6715CEF3
An easier book from the same author is
Algorithms unlocked- Cormen
http://libgen.org/book/index.php?md5=ded655a8c87eda65c81f064aade1f901
Probably the best book for a newbie once you understand the basics of programming.
If you can read these books and understand most of them, you'll have the foundation for almost any math and computer science subject, say
analysis
numerical computing
combinatorics
probability and statistics
abstract algebra
artificial intelligence/machine learning (requires prob. and stats)
cryptography (abstract algebra/number theory required)
graph theory
and cool shyt like that which can land you a sweet job. Just know that reading math is not like reading a novel, and there's a lot of shytty math books out there so don't get discouraged and always check amazon reviews.
If you're reading a math book and it's too abstract, then get a simpler one. I've read like 4 books on linear algebra and if I would have started with the last one I read I would have gone crazy. There's different stages to learning math and if it's way too complicated for you it doesn't mean you're dumb it's just that the book is from an advanced standpoint and for people who already know most of the subject, so you need a more concrete book with simpler examples and shyt.