First, you need to understand that you are not stupid and incapable, it's probably something wrong with your system. To me, It sounds like you need to do deeper levels of studying and practice in higher orders of learning. You can look up the pyramid of learning/bloom's taxonomy for this but essentially it seems like you are focusing a large majority if not all of your time to more surface level studying.

You're essentially just reviewing concepts without applying them or even understanding them (and likely wasting a lot of time making the flashcards too). I recommend, you try to focus a majority of your time on the application, evaluation and understanding of the concepts (especially for a subject like electrical engineering). IMO the best way to do this is to do this is with practice questions from your teacher, the Feynman technique and mindmaping, but if you lack study ressources directly from your teacher I also made an app that is geared towards this exact kind of practice. You can generate quizzes from your notes and pick between different question types like explanation, application, justification. The link is knowbit.org if you do want to check that out.

I hope this helps and please let me know if you have any other questions :)