Synonyms of credulous in English:

gullible, naive, impressionable, trusting, over-trusting, over-trustful, exploitable, dupable, deceivable, easily deceived, easily taken in, easily led, unsuspicious, unwary, unguarded, unsceptical, uncritical, unquestioning

innocent, ingenuous, unworldly, inexperienced, unsophisticated, artless, guileless, green, as green as grass, callow, raw, immature, childlike, wide-eyed, simple, ignorant

informal wet behind the ears, born yesterday

rare incognizant, nescient