gioco da ragazzi znamená v Angličtina

child's play▼(something particularly simple or easy)
noun
[UK: tʃaɪldz ˈpleɪ] [US: ˈtʃaɪldz ˈpleɪ]

piece of cake▼(simple or easy job)
noun
[UK: piːs əv keɪk] [US: ˈpiːs əv ˈkeɪk]