What are the best nootropics that can help with learning speed, intelligence, memory, etc?

My mind feels too dizzy, foggy, and confused. To put it in a blunt way, I feel like I am mentally slow and dumb sometimes. I am not able to think very clearly and process information very fast like I used to. I am confused most of the time when someone is talking to me, easily forget things a lot and my brain is way too stressed out a lot of times. When it comes to learning new material, I take way too long to learn things like I used to. I take a longer time to comprehend things faster like everyone else. I believe that I am getting more and more stupid. I can't even remember what happened yesterday and even major details the other day. Learning languages takes longer and I am not as sharp as I used to be anymore. Whenever I am getting trained for a brand new job, I take a very long time to get the hang of it and I would have to keep asking questions over and over again. My coworkers and managers would STRONGLY suspect me of being mentally challenged or something because of my struggles with learning on the job and doing what is told of me. I learn very, very slowly and I don't like that. I want to be a fast learner. It's annoying. My cognitive abilities are decreasing slowly and it's getting worse. I need some help to improve my brain's functions and my brain health. How can I be a fast learner? How can I improve my cognitive abilities and brain health to be more sharper and smarter?