To improve your communication skills in English for an interview 

Practice

• Practice answering common interview questions with a friend or family member
• Record yourself to identify areas for improvement, such as pronunciation and grammar
• Practice using shorter sentences

Build your vocabulary

• Build your vocabulary by reading, watching movies, and immersing yourself in English news
• Start a vocabulary book of useful words

Be confident

• Gaining confidence can help you overcome nervousness and stage fright
• Speak in a confident, friendly tone
• Establish that you have credibility or authority