Hello Hela
I'll parse your sentences as follows.
The parenthesis […] means the entity is a noun phrase. And the underlined part is an adjective phrase. Please understand sometimes a noun phrase includes an adjective and sometimes an adjective phrase includes a noun phrase.
1) A beautiful young girl won the race.
[A beautiful young girl] won [the race].
2) The French boy will leave in June.
[The French boy] will leave in [June].
3) The very little boy broke his leg.
[The very little boy] broke [his leg].
4) The old building opposite our school is being pulled down.
[The old building opposite our [school]] is being pulled down.
5) Someone remarkable saved her uncle’s life.
[Someone remarkable] saved [her [uncle]’s life].
paco