Iam a little confused about this text. I've realized that since may 22th there was a change of behaviour in the graph , recovering its normal values again on august 21th. it seems as if had been a problem. I would have noticed if I had review this graph before. there was a change or there has been a change or there had been a change...¿? I had review or I have been review or I had been review ¿? What they are ok ¿?

difference between follow and follow up What is the diference between follow and follow up ¿?

there was vs there have been

Hi, im not very clear which i have to use  "there have been vs there was"

Ha habido un problema con la reserva del hotel :

- there was a problem with hotel booking

- there have been a problem with hotel booking

Hubo un problema con la reserva del hotel:

- there was a problem with hotel booking

- there have been a problem with hotel booking

thxs

difference between "had to do" and "should have been done"

Im not clear about the difference between:

- I had to do it

- I should have done it
- I ought to do it

To say: tenía que haberlo hecho

Difference between "have just done it" and "just did it"

Hi,

  i'm not very clear what the diferrence is between :

 - I have just done it

- I just did it

txs a lot