An intermediate plateau is either caused by the reality of not making progress, or the perception of not making progress.
• If you're not studying as much as you were in the past, then the plateau is probably real. The solution is to go back to studying as much as when you felt like you were making progress.
• If you are studying as much as you were in the past, then you could still be making progress, but you're not perceiving the progress like you used to. You've built up a resistance to sensing progress, like a resistance to a drug. The solution is to keep working, and have faith that you're learning.
Either way, study every day, write as much as you can, listen as much as you can. Change your habits, listen to English versions of the news, newspapers, websites, change your computer settings to English. This is immersion.
Self-talk. If you find yourself thinking in Hindi, stop and think in English. This is not really thinking, it's internal dialog, or self-talk.
After interacting with someone in Hindi, if you have a few seconds to spare then repeat the sentence in English in your mind. This doesn't work in a conversation when you have to listen to the reply, but it'd work buying a ticket, or greeting a colleague in passing, or for the last sentence of a conversation, or answering a question. That kind of thing.
Are you making an effort to remember things? Are you actively committing words to memory? If so, how do you do it? Do you use mnemonics? Similar sounds in Hindi, inventing images, etc.