Why do I forget everything after a few days?

Words you only recognized were never stored for retrieval. Saying them out loud on return visits is what makes them stay.

Because recognizing a word once is not the same as storing it for retrieval.

Return visits beat first visits

Memory is built by coming back. Five sentences revisited on four different days will outlast forty sentences seen once.

Say it, do not just see it

Speaking a sentence engages far more than reading it. That is why ten minutes of out-loud repetition sticks better than an hour of review.