One of the most difficult things we have while learning a new language is to change the way we pronounce, especially the stress (
acento/golpe de voz). Have a look in your English books and you'll see it's something quite common in the pronunciation section.
If you want to "sound natural" you should pay attention to where the stress of the sentence is. The general rule is that you stress on those words which are really important in meaning within a sentence or the ones you want to emphasise; e.g.:
What are you doing?
I'm working at my office At your office?It's my office
If you're interested in knowing some more details and some oral examples, go to this link of
Hablar mejor en inglés; click
here to go directly.
There is also a long but useful explanation on
BBC Learning English. Click
here to visit the page
Hope it'll be useful. See you at school soon!