First, try to relax.
The course providers do not want to catch you out during the interview. They are simply trying to assess whether they think you will be able to complete the course successfully. Most reputable establishments are reluctant to fail people, because this might be seen as a sign of their fauiure to train properly, so they try to accept only people who, they feel, have a good chance of succeeding.
Also, some people just do not possess the personality or academic ability to complete the course succssfully, even with the best trainers in the world. Reputable establishments will not accept such people on the courses .
So, they will just be trying to find out something about you. They will almost certainly want to know why you want to become a teacher of English, what ideas, if any, you have on what you think the role of a teacher is, and whether you have had any experence of teaching in any form.They may well be interested in why you chose their training establishment.They may also ask you some questions about your knowledge of English.
Try to give honest answers. If you don't know the answer to a question, say so. Don't forget that if you knew all the answers, you probably wouldn't need the course anyway.