what does it mean - Nos llevamos 3 años y media?
There is an age difference of three and a half years between them. (That’s how I read it)
the construction “llevar + time + gerundio” means doing something for a certain time
You could tanslate it as “We took three years and a half …”
Another example: "Llevo un ano aprendiendo el espanol. "(I am learning spanish for one year)
I agree with Cosmo678, yet in the context of the above lesson it is an age difference the person is talking about…
ad SanneT: You are absolutely right. They are clearly talking about an age difference in the dialogue. You would not use “nos llevamos” if you were referring to an activity you have been indulging in over a certain period of time but only “llevamos …”.
Llevamos tres meses trabajando en esta empresa. You would not say “nos llevamos trabajando…”.