what happens if the brands are from country where it is not possible to pay in crypto currencies?

you won't have to pay directly with crypto currency, your crypto will be swapped with coupons or gift cards and pay for services or goods with it.

All that will be done on ethereum blockchain?Is Ethereum blockchain fast enough for that?

Well I hope it will be, if you remember what happened with Crpytokitties! If that happens with Zeex and gift cards that would not be so good Cheesy

Ethereum blockchaion keeps improving and evolving,so im sure everything will be fine.

I'm sure it will, there must be a good reason that almost all new projects are developing on Ethereum blockchain.