Well, you can clearly learn because you are writing replies here, so you are able to read, form an opinion, and provide a response!
I just don't think you've found the right method to learn maths, and this might be because you haven't found the right incentive to.
Why not try a hobby or sport where numbers/maths are important?
Some sports have quite complex scoring, and some hobbies need numerical/measurement skills, e.g. sewing, crafting, etc.
Once you've built your confidence back up, consider finding a local tutor to help. Some local voluntary organisations also have this service.
Regarding the police. Yep, numeracy and literacy are essential, as are motivation and self-discipline.