23rd September

I'm Laura from Rome. The  weather  was  good  this morning.  It was sunny. 

My family consists  four  members: my mammy,  my daddy, my  brother  and I.

 This  summer  I went  to Sardegna on holydays. It's  a beutiful place ;)   

Basically, there's nothing grammatically or lexically wrong with your paragraph!! I only made some stylistic changes, which sounded better and more natural to me! :)

23rd September

I'm Laura from Rome. This morning in Rome there was a good weather the weather was good, there was sun it was sunny.
My family is composed by four peopleThere are four people in my family: my mother, my father, my brother and I.
This summer I went to Sardegna on holiday. It is a beautiful land country!