One of the difficulties language learners face is knowing which form of a word to use. Do I say, "difficult" or "difficulty"? A non-native speaker might say something like "I have a lot of difficult to do that," using the adjective instead of the noun form. How do we know when to use which? We don't necessarily need to study a lot about word forms. Native and high-level English speakers can often tell from context what part of speech a word is. Take, for example, the poem "The Jabberwocky" by Lewis Carroll.
"Twas brillig and the slithy toves did gyre and gymble in the wabe..."
Although you may not have the slightest idea what those words mean, you may still be able to tell from the context how they are being used. For example:
"Twas brillig (a thing) and the slithy (description) toves (somethings) did gyre (do something) and gymble (do something else) in the wabe (place)..."
Since things are nouns, descriptions are adjectives, and actions are verbs, advanced speakers know intuitively what word forms to use in a given context.
This isn't something that newer language learners can do! But they can, with lots of exposure to the language, develop awareness of how words are used in context, and thereby know which form of a word to use.
There are 2 steps to this, of course. The first is knowing which word form you need, the second is knowing what that form is. Here are some suggestions for developing these skills:
For step 1:
For visual learners, those who remember best by seeing, try reading a challenging but interesting paragraph until you get the meaning. Then read it again focusing on how the words are used. Read it again out loud and listen. Notice the functions of the words used. Notice words which represent a place, thing, idea (noun); action, condition (verb); description of a noun (adjective); or description of a verb (adverb). This will help you to develop awareness, which you can use to self-correct
If you don't love to read, you can do the same thing by listening. This is useful for auditory learners. Listen to a 2-minute interview or monologue for meaning. Then listen again focusing on how the words are used. If you can't replay, try switching your attention as you listen from meaning to form.
For step 2:
Read or listen for meaning as in step 1, then when you listen/read again, focus on the endings of word forms.
Make lists of word endings for nouns, verbs, adjectives, and adverbs. For example, nouns have lots of typical endings, or suffixes, like -ment (encouragement), -ity (familiarity),-tion (integration). Adjectives have endings like -ful (beautiful), -al (political). You can familiarize yourself with suffixes for common words by listing words with same endings in columns, writing some simple sentences with them, and reading the sentences out loud to yourself.
There is no quick fix to learn English, but by relaxing, immersing yourself, and noticing patterns, you can become an excellent communicator in your adopted language.