what can I do to become an H & M model?

Modelling has absolutely nothing to do with Theatre & Acting.
Try asking in the Beauty & Style section?

But hundreds of thousands of kids want to be models (heaven knows why - it must be the most boring, pointless job on the planet) so the chances of you ever getting paid modelling work is really small.

Get trained for a real job, at which you have a chance of succeeding.

being an all rounder is always useful even if it might not seem required. and being a model of a clothing shop, you need to appeal you characteristics and not your appearance. with stuff nowadays, people can be Photoshopped and stuff so appearance lost it's dignity, but rather, you need to emphasize on your characteristics so what they see opportunity in you.
here's an example:
if there was a beautiful person went to an interview for a model but had a boring characteristics, they wouldn't know what she should wear, but oppositely, if you give off a very summer feeling all year round, they know what they want you to be in, and would see chance in you