Friends, it is normal that it is so difficult for me to study, but so much?

I don't study anymore I stopped doing it in 2016, my problem is that in my studies I don't understand anything I can't remember anything I forget everything, the most I can achieve is memorize but what I can memorize is very limited, I always I have had this problem of not understanding anything they explain to me and forgetting everything, this cost me the dismissal from a company.

They had sent me to learn some theoretical concepts and I could not understand them.

I tried to memorize them but I forgot parts of them.

Friends, it is normal that it is so difficult for me to study, but so much?
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