If you study but cannot remember what you learned, the problem may be that too much of your studying is recognition rather than retrieval. Rereading notes can make material feel familiar while leaving recall weak. Memory strengthens when you close the book, try to produce the idea yourself, discover what is missing, correct it, and return to it again after time has passed.
Replace part of your study time with active retrieval: explain the topic without notes, answer questions from memory, recreate a diagram or method, and test yourself again later rather than immediately. Keep the difficulty manageable, but do not remove the effort entirely—the act of retrieving is part of what makes later retrieval easier.
Use the Study & Learning Methods Hub for retrieval, spacing, revision, and transfer. If the material still will not hold because an earlier concept is unclear, move into the Diagnostics & Recovery Hub.