A2A. Algorithms is the art of breaking down a problem into very simple instructions understandable by a computer. Again, everyone cannot be good at everything: Brijesh Kumar's answer to Can anyone achieve anything he wants (e.g. GATE examination)? Does aptitude matter or perseverance and attentiveness is key?
I don't think any specialized math knowledge other than basic arithmetic is required for understanding basic algorithms and basic data structures.
So, you can try learning algorithms from a basic book. I am not a computer science major, so I don't remember the name of a basic book for algorithms. Algorithms by Cormen (CLRS) is not a basic book. Try it for a few months beginning with simple algorithms and try to develop on that foundation. If you are still unable to understand after a couple of months of trying on your own, you can try taking some classes. If you are unable to take classes or even after taking classes, you are unable to understand, it is better to focus on app development (something you are good at) rather than waste time learning algorithms.
An anecdote: In my school, I never got highest marks in any subject, but I always got highest marks in Computer Science (which mainly consisted of writing algorithms and simple data structures, such as arrays), sometimes much higher than other students in my class, because I "got" computer science whereas other students did not "get" as much. Whereas the other students "got" other subjects better than me. So, we have been gifted with different strengths, because otherwise life would be unfair if one person was good at everything and others were good at nothing.
It is nothing to feel bad about. You are good at app development which I (and most others) know nothing about.