To master your Russian, you need to learn how to tell the story in Russian. At advanced level your story will be a spontaneous narration of situations of situations happening in your life. You will start retelling the story by setting up the scenery, describing people and making the event chain. In order to do this, you will need to come up with sentences that are formed from word combinations and phrases. To connect the phrases you don’t need to think about grammar rules in an ideal Russian speaker world. But you are learning, so, when you are telling your story, you will be thinking which word you should use and how to change this word to link it with other words in a sentence. If you start practicing retelling the stories you will soon notice that the words you are using quite often repeat themselves. Many phrases can be transferred from story to story. At the same time you will start looking for synonyms and opposites to expand your language vocabulary.
Вечером мы пошли на концерт.
Я пошла, он пошёл, вы пошли
If you stop for a minute after you said this sentence and start changing the verb connecting it with different pronouns and adding different context you will grow language wise.
Мы пошли на концерт, после того как купили билеты. Мы пошли на выставку, после того как увидели рекламу. Я пошла в библиотеку, чтобы подготовиться к экзамену. Он пошёл на вокзал купить билеты.
I would recommend you when you are telling the story, stop after sentences and change them. Change verbs, change pronouns and conjugate, change location nouns, change purpose nouns.
I want to suggest you reading Russian children fairy tales because they have short plots and intriguing storylines. The unfolding plot keeps you reading it and retelling it.
Read “Храбрый портняжка» (a brave tailor) by Brothers Grimm in Russian. This is a fable about an inventive and smart character, who tricked people into believing into his magic powers.
You need to read this story, first. Read it to yourself. Start telling it to yourself alone. Peep into the text while you are telling it. Practice it several times. Then find a Russian speaker and tell this story to a Russian person. Create two versions of your story. The first is a detailed retelling, the second is a summary.
Then start telling what happens to you in everyday life in Russian as a story: first to yourself, then to a Russian speaker.
Finally, write your own story in Russian. Become a writer of imaginary events in Russian. The thoughts and phrases will come from within. It will not only improve your Russian and will make you look up for new words in a dictionary, but also will make you feel more confident by telling everything you can think of without limiting your language expression.