In many ways it is important that you know that you CAN NOT TRUST (CONFIAR) YOUR ENGLISH TEACHER to really speak “normal” English with you.
When English teachers come to Spain they tend to reduce their accents as much as possible and they avoid using colloquial terms because they want you to be able to understand easily. This is a great approach because it makes you feel more confident which is wonderful. The only problem with this is that when you go to the UK or the US, and you suddenly start speaking with “true” native speakers, you quickly notice that these people don't speak the same way as your English teacher!
There is no easy way to resolve this problem other than expose yourself to as much English as possible through a variety of media channels. Remember, that your English teacher remains a vitally important part in your ability to learn English but you just need to add extra elements onto the core focus of English classes.
Hope that helps!
Soy el director de Daniel Smith + Partners. Tengo más de 10 años de experiencia enseñando inglés a españoles.