My sims 3 crashes after 30 minutes playing on my macbook air

Angie1244​  Your Mac's graphics chip is actually under the minimum requirement for Sims 3.  That doesn't mean you can't play, but performance may not be great no matter what you do.

Having said that, it helps on your class of hardware to turn lighting and tree detail down to the minimum settings.  It may also be best to play in Sunset Valley rather than Bridgeport, as the latter has some issues that are not necessarily fatal but can push the game over the edge when it's already struggling.  If you're bored of SV, Riverview is free on the Sims 3 Store site as long as you're registered there.

Separately, please remove the image you've provided, as it contains your laptop's serial number.  That should never be shared in public.

Thank you so much for your kind answer! Yeah, I decided to play directly on Sunset Valley after a deep research. Is it a good idea to play both at the same time or only focus in one of the two worlds? Thx again!

Angie1244​  You can have as many saves in as many different worlds as you like, and switch among them whenever you want.  Your unloaded saves or worlds have no impact on the one you're playing.