A word like por favor sounds like a W to German ears, but what is actually spoken is a B – just so quickly that you hardly hear it. The same goes for botella or playa: spoken slowly they sound different from normal speed.
In the stories Gregor sticks to one version each time, because when learning you should only ever learn one thing at once. You then pick up the exact pronunciation from Elena. Both versions work – in Spain you will be understood either way.
Simply listen to Elena often, like a child hearing a word hundreds of times from its parents. Gregor shows you how the sentence gets into your head in the first place, Elena how it actually sounds.