Hello Caremel
Thinking of a topic is the hardest step .. but let me suggest :)
You may talk about chocolate.. and some interesting facts about it
As for the materials, you can of course use pictures and other stuffs relating to it
or you may talk about an incident happens to each one of you during your childhood and attach pictures and some of your old clothes if you have
The most important thing for teachers is not the topic it self, though it could be for some, but your fleuncy and occuracy
Be confident
Practice and practice
have someone to hear from you to correct your grammatical and pronounciation mistakes
prepare a small paper including hints in case if you forget
Good Luck
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