Improving your English communicative ability is about first knowing your goals for learning English and then establishing clear steps for reaching your goals. Once you have done that, focus on fluency rather than accuracy; then work on skills that will help you convey exactly what you mean to say.
Get a good book on the gestures that native English speakers employ. This book should be written by an expert in your own language. From this you should gain an understanding of the cultural cues behind the gestures and the norms of their use.
Watch the video again in short 20- or 30-second increments, and try to repeat as closely as possible the same gestures and intonation. Repeat until you are confident of your performance. If possible, record yourself performing the dialogue. Compare your performance to the original and identify your weak points.
Become confident in using your hands when speaking. You will be amazed at how much you can communicate with your hands. Note that native speakers use such hand gestures in coordination with verbal communication to more clearly convey ideas.
Speak with confidence. Remember: native English speakers make mistakes, too. One of the key differences between native and non-native speakers is how they deal with mistakes.
If you make a mistake when speaking, DON'T WORRY. Watch the facial cues of your conversation partner to see if they understood what you intended to say. If you are unsure that your meaning has been clearly conveyed, ask a question such as "Did that make sense?" or "Am I being clear?" This is an example of a clarification strategy.
Study synonyms and antonyms, and practice explaining complicated ideas in simpler words. The key to improving your communicative competency is being understood, in any way possible—it is not to appear "perfect" (in fact, there is no such thing as a perfect English speaker).
Find a conversation partner—someone who will speak English with you for about an hour or two a week. Improving communicative ability will take time. Have patience. Reward yourself frequently for the small gains you make. Be sure to speak only English with your conversation partner.
Choose a word or two and repeat them to yourself throughout the day. Don't do this in front of other people, though!
Identify words that are frequently used in subjects that interest you.
Choose five of these words every day. Before going to bed, write the words three times on a piece of paper, and then say each word aloud to yourself three times. Finally, reread the three words and silently repeat them in your head.
Study the same five words when you wake up in the morning, using the same pattern as described in the previous step.
Carry a few flash cards with you throughout the day. During a free moment, quiz yourself with the flashcards or simply review them. Research has shown that a student must use a new word about 15 times before being able to remember it consistently.
Record yourself saying your target words and their definitions. Carry this recording with you and listen to it at various times during the day, preferably when you are doing something that does not require much attention, e.g., during your commute, when doing housework, while exercising.