What if Effective Communication & Organization?

Got Mid-year feedback, and had a few people do informal feedback as while I had strong strengths, the biggest negative and consistent topic was communication. Basically punctuality, understanding of assignments, communicating delays, etc. My intellect and abilities are all there, its the back-end internal admin stuff holding me back. What does effective organization and communication look lik  in terms of getting work done? I feel that I'm also super slow, so I'd imagine that would also play a factor. I just feel that its hard for me to switch topics and stay organized in my head.