You learn words and grammatical forms by repeatedly encountering them in context, meaning these things will be apprehended only once they come up naturally enough times.
Once you know something easily you can focus on other aspects that are more unfamiliar, and hence gradually improve your understanding of the language.
Don’t be discouraged when you encounter unknown words and forms or forget things you thought you knew — it’s a natural part of language learning. You will require a lot of repetition before something truly sticks in your mind.
Repetition happens naturally as the most common words and forms are encountered frequently.
Drills such as ﬂashcards are designed to repeatedly prompt you with the same thing until you remember.
You can also get repetition by reading the same piece of content multiple times. It is also useful to review activities, lessons, or content you covered a few days or weeks ago.
Most of your initial grammar learning comes from your beginner and intermediate courses, helping you understand the core verb/noun forms and the general structure and logic.
From there you can reﬁne and improve your knowledge using large amounts of input. Learners also drill grammar using ﬂashcard sentences.
Key tip: Do not rely on learning grammar rules
In general, learning rules is a poor way to acquire a language. Remember the principle “Use the language in order to learn it”? While rules are useful to know, learning only happens when you use the language.
Rules and other aides such as conjugation tables should be used as a stepping stone to help you understand meaning in context.
While it is ideal to use direct explanation only once before you use content, it is completely acceptable to go back to the explanation to help you if you can’t remember.