Language learning can be a slow process. Unfortunately, there is no magic formula for you to follow to go from the long intermediate plateau to an advanced speaker. You may simply lack the language exposure needed, or you may have some fossilised issues you need to focus on removing.
The short of it is, if you are not actively studying to improve some aspect of your language abilities, your progress will be slower. Spend some time figuring out your deficiencies and working on improving them. What you do will depend on what your problem is, though more input will always be good.
Keep in mind that languages are large, and filled with innumerous words and phrases that are seldom used yet are an essential part of native speech. Think back to the phrase above: “the short of it is”. If you are a native English speaker, you likely didn’t notice that it is not the normal usage of the word “short”, it was simply a natural phrase you sometimes encounter and might use yourself occasionally.
There are many ways to say the same thing in English, and there are many thousands of unique phrases and different usages of ordinary words in your target language, too, that are both different and applied differently, which must be encountered with sufficient frequency for you to absorb and later produce to get to an advanced level.
Native speakers have the advantage of huge amounts of input to get used to them, so don’t expect yourself to shift off a plateau towards a new level without a lot of input yourself. In short, don’t be too hard on yourself.
