Can I be good in field of mathematics in college or others are smarter?

In the year before high school, I was well in math. Not in a famous school, & studying less ,even didn’t answer exercises in my notebook, unlike others, but remember like one time, we were tested (maybe hard) could open notebook/etc: I could get the best score, in spite of my lame notebook.
In 1st year of High school,I entered a more famous in city school. And I showed I am one of best students, even in math, I was top 3. I did very well in that year in school.
In second year, I became famous in class and maybe school for outstanding math skills. I remember I did study some math, and maybe, unlike others focusing on questions, I focused on formula and rely on my own thinking instead of similar questions. For instance, one time, I once read more examples and I saw a decline. So, then, I got back to my own way of study and I gained back. Not surely this, but some times, I was not best (like once I did best but doubt and deleted the true answer which would gain me %100 if wouldn’t delete it), but totally, I was way better than others (for example, once I gained 90% while nobody else (or some times only one) could get above 50%. All but me failed it means… In that year, I started learning C programming, too.
In third year, I declined, because I totally left studying. I did no study really. Many were attending private class and I was poor was a reason I be hopeless, too, and the teacher hoped people go to his private classes for benefit of $ and so didn’t teach well, too…
In fourth year, nobody was perfect, I was even worse due to really no study at all.
I learned C# and did well in programming at 19. (programmed an NMS which usually more pro do)… I am good in programming more than these.
I am 30 now, but want to study mathematics, as it will help me in cs, too, and I like it, too. Are others smarter in it???

Thanks!

Yes, there will always be somebody more smarter in some topic. People can learns from others as well and this mean not just faculty but sometime students too.

Mathematics can be good to learn for all ages but it depend on what if anything you want to do with it.

You can learn language of mathematics for many reasons and CS is surely as well reason as any.

But it will be tough to try to gain entrance to Columbia as a 30 year old if your goal is an undergrad mathematics degree, and you are so far removed from high school.

Maybe you want to learn English better if you can so other people can understand better