How can I improve my English from levle B1 to C1 in a month
Im not going to write for too long as this is quite simple. Stop reading and practicing your textbook and stop trying to memorize weird , unusual , only-used-every-ten-year words. I know it feels like your problem is with words and grammar but in fact its not. I know because I ve been there. Spend 4 months taking a course and hundreds of hours to get 60 out of 100 in my C1 exam and stuck with 56.
Then I took it again a few years later , didnt even attend the class and i was the only student who have passed the exam with a 72. I am quite sure i missed all the weird grammar and words but i was already developed the skill of “Thinking in English”. I didnt even spend practicing my writing for a second neither.
So basically you need to be able to think in English. Best and fastest way to do this is to put yourself in the most discomfortable position possible and stop thinking and talking to yourself in your native language.
For speaking always speak to yourself loud and think in English. Imagine you are speaker and give speeches in English. Topic or your knowledge doesnt matter. Just speak. This way you will practice making sentences fast , articulating your thoughts and also you will find the LEAKS in your ability to speak English. Whether words or grammar. You will see where you stutter and what you dont know. What you cant explain. Just google them. And do this ALL DAY. Your family will think that you are crazy. But thats the only way to be able to speak. You will see immense difference in short time.
For everything else (listening , writing , grammar , vocab etc.) stop with the subtitles. Get rid of them. And watch videos in English about something that interests you or entertains you or useful for you. Never use subtitles. Your brain works with magic and if you force it to understand things , it will understand things. I would especially suggest watching videos with instructions because they are the hardest to comprehend without fully hearing the sentences. I suggest fitness youtubers for this and especially Athlean X. Both very useful, and a clear English is used in the channel. Also watch Gordon Ramsays stuff. Very clear English and hella lot fun. Mix it with videogamedunkey which is also fun, channels like crashcourse, school of life, valuetainment, charisma on command etc. to challenge your brain to comprehend the story. Then read a lot ; reddit , 9gag , youtube comments , quora are all great way to get used to everyday and actual English. And also great to get familiar with new types of sentences. Use whatever floats your boat. But never skip the words you dont know and chech them. Last but not least write a lot of comments confidently on every chance eventough you have no idea what you are talking about. Aim is to express your opinion. You will be corrected harshly and learn very fast.
As a side note : Grammar and vocab are just polishments. You can articulate all your thoughts with very simple words and sentences by using linking words like “by, to, and etc.” a lot. Not preffered but gets the job done. Good luck! :)