My opinion is similar to the other commenters: you are not stupid or dumb for not understanding certain subjects, it's far more likely that you didn't have a proper teacher from where you could learn the needed tools to solve complex math problems.
I'm currently working on my math skills as well - I'm trying to learn computer science by myself, which is obviously hard and it's driving me insane. What I learned so far is that the adquisition of complex skills takes a lot of time: a 2-week course will not teach you much, it is fast-paced and the organization will surely be all over the place.
Before taking interest in computer science, I studied web development for about four years in total. It took me two whole years to truly understand how programs, data structures and algorithms work, along other things. And to this day I still don't know as much as I wish to. The first years were rough, since I wasn't familiar with anything related to computers, other than to use them for games and such. I had to watch how others wrote scripts and webs in less than an hour or two, while it took me whole days to comprehend what the hell I was even doing.
While my grades were somehow decent, my understanding was not to the level of the other students.
My point is - most of the students were already familiar with the concepts, while I wasn't. The teachers weren't willing to sacrifice time of their classes to help me understand, if I failed, the immediate suggestion is that I wasn't good enough to be there.
By the time the third and fourth years came along, the script changed drastically: since I took my time to understand the material and programs that I worked with, when my brain finally processed it, my programs went from absolute garbage to mild garbage: which may not seem like much, but programming is hard. I gained enough skills to have fun while programming, instead of being constantly overwhelmed by it.
I know my comment is pointlessly long: but what I wanted to say is that it's not your fault if you are not familiar or struggle with complex subjects. They are complex, after all - understanding them takes a lot of time, and mastering them takes even more. That doesn't make you less than anything or anyone else - you have a lot of value, and deserve many good things.
It takes courage to recognize that you are not currently skilled at something: many would opt to just ignore their own deficiencies.
The thing is: a two week course is useless to determine whether your skills are "good enough" for you to take a path or another.
Of course your skills are not good enough yet - if they were, most likely you wouldn't be in that course to begin with. That isn't necessarily a terrible thing - you are not dumb for not knowing complex subjects, it just means that there hasn't been enough time dedicated to the analisis and deep learning of the subject. This doesn't mean that you are unfit to go to university at all. Although I completely understand how awful it feels...
Have you considered that you're not dumb, but people commonly teach math badly? They teach it as mindless manipulations, rather than the concepts &
mental models themselves?
This, to me, seems completely true. Ever since I was a child, I had always been called dumb by teachers and other students for not doing well at math - I always struggled and it would take me a lot of time to understand what others already knew.
Now I realized that the approach I was taught was a completely horrible one: each mathematical operation and problem that I was taught as a child was seen as an individual and mindless operation, disconnected from other concepts and models that I already knew - thus my brain processed it as something that I had to "inherently" know how to do already, instead of applying every tool that I had already learned beforehand. A set of mindless operations, that turned me into a mindless individual sitting in a chair - which plummeted my self esteem by making me think I was the dumb one (which I was, but for entirely different reasons... Not related to my math skills at that time :P)
I carried on with that mindset until fairly recently.
Now i'm currently making my way through an old book called 'Notes on Structured Programming' by Edsjer Dijkstra - the first ever dutch programmer. I thought I was dumb, but as it turns out, if I take my time to research and understand the problems presented in the books I read and in the programs I write, I can actually do maths to prove the efficiency and correctess of the algorithms I write, which is something I never thought I'd achieve.
I'm not an exceptional individual - I'm as common as they get: yet, if I take my time and try to understand the concepts I read, my mind absorbs them sooner or later, and uses them in a logical way instead of doing mindless operations.
Math is a wonderful subject. It doesn't have to be a depressing and awful thing to go through - but the institutions are stubborn in making it so.
It's not your fault - although I understand completely why you feel this way: I also feel I don't quite belong anywhere. It's crushing, honestly.
I don't have any resources to list since I don't know entirely which mathematical problems you are struggling with, so I'd rather not recommend random things I happen to like. But... I'm gonna do it just once:
If you are interested in computer science, I recommend this amazing website called
www.progamming-motherfucker.com
I know. Very funny name, but it has a resource list with tons of programming books, websites and other things for tons of programming languages. It's not a resource list meant for those that want to "learn X in 12 hours, 2 weeks or 6 months", as it is so common these days, but it's meant more as a toolset to gain as time passes, or at least I view it as such.
I posted a really long reply. Sorry to whoever actually made to this part. I didn't expect to write so much..