Make English your default language. Tongue twisters are series of words that are difficult to say quickly. Try to memorize simple words.
Repeat and revise
Start watching English channels and English movies. Observe the words delivered by the actors/ news anchors. Repeat and revise the words in the correct accent.
Assign yourself a topic and start speaking on it. Gradually you will notice a more confident and improved self.
Play word games on your mobile phone. This will improve your vocabulary.
Read English Newspaper
Newspapers are a good place to find passive constructs. Read through an article and see if you can find the passive sentences.
Listen and sing English songs
If you are a music lover then listen to English songs. Repeat and sing the songs again and again.