One of the quickest ways to win in English speaking tests like the G.B.C., IELTS or TOEFL, is to say what you can.
Accept that your native language level is higher than your English level, and that's ok. Focus on the language you already have.
This is a simple idea, but it can be hard to put into practice.
The language gap
When it comes to transferring ideas from your native language into English, you can’t say it all in English—so don't.
Your first language ability is higher than your English ability. There may be ideas or topics that you can talk about in your first language, but you can't talk about in English. So in speaking tests, avoid ideas that you can't produce well in English.
Imagine a high school baseball player who wants to play in the Major League. That is a great dream. What if he wants to play in the Major League today? Well, the answer is he can’t. He has to wait. He has to keep practicing. Likewise, you also have to keep practicing to say some challenging things.
The language gap has a second point—English is simply different from your first language. There are many words, phrases or ideas that don't translate easily or directly.
Use what you have
Your English ability depends on the subject. For example, if you have studied business English, then use business English in your speaking test as much as possible.
This means, if the test interviewer asks you to talk about where you live, then you should choose carefully. You may want to talk about efficient transportation or traditional cuisine. In your native language that would be fine, but how much experience do you have talking about those topics in English? If you don't have much experience, then choose an answer that suits your strengths now. If you have experience talking about business, then why not talk about your city’s economy?
Here's a metaphor: imagine you are going to cook dinner, you look around your kitchen and you see some basil, some garlic, canned tomatoes and pasta noodles. Should you make hamburgers? No! You should make pasta. What if you really, really want to eat hamburgers? Well, if you tried to make hamburgers with those ingredients then you would end up with some very strange hamburgers. Use the ingredients you have. This means, in language, you should use your words, phrases and sentence structures to make the best answer you can make. Choose based on what you have, not what you want.
Of course, in your lessons, you should do the opposite. Get new words, practice new grammar, experiment with tough ideas.
But a test is a performance, so make the best answer with the language you already have.