Je peux pas t´assurer que tt est correct mais bon, je vais essayer de t´aider...
I sing since I am 7 years old.
I have sang for 7 years.
Where did Holly grow up?(la, c obligatoirement ça car holly et Sydney precise la totalite de la question a poser)
ex : Did you visit your grand-father? ( ya rien de precise ds la rep, dc tu peux adapter je pense)
ex : Did you buy the book you were looking for? ( idem)
My mother bought me a mouse last week.(last week marque le fait que l´action se passe ds le passe et qu´elle est terminee, elle l´a achete, dc preterit)
They have discovered human bones that were in this garden for centuries. ( la, je suis pas sur mais comme la premiere, c obligatoirement du preterit, la logique professorale voudrais que la deuxieme soit au present perfect!^^)