avoid duplicate content

Hi, I add every post on my website to a category. every URL looks like that: https://teesvg.com/downloads/teach-love-inspire-svg-red-for-ed/
and every category looks like that:
https://teesvg.com/downloads/category/teacher-svg/
when I search my keyword on google, every time I get the 2 results: the post and the category so it’s duplicate content.
I want to ask how to avoid duplicate content in my case, it’s important for me to add every post to at least one category.
I do SEO for every post and for every category.

My second question is how to do if I want to add a post to two categories and avoid duplicate content in my case?. I can’t use canonical URL because I always have unique URL for my posts like that:
https://abcd.com/downloads/abcd https://abcd.com/downloads/efgh…
and not like that:
https://abcd.com/category1/abcd
https://abcd.com/category2/abcd
thanks