You have to spend time to build your mathematical foundations. You have to get familiar with it through problems and exercises. I don't think there are shortcut

You have to spend time to build your mathematical foundations. You have to get familiar with it through problems and exercises. I don't think there are shortcuts. If you don't have the foundations it's wasteful to spend time trying to work out academic papers and such. Bite the bullet and start from the beginning, it'll pay off over time. It will also allow you to go much farther. Even if you manage to 'understand' what a paper is saying, without the background you won't be able to do much other than replicate it.