how to say “naive” in Hebrew
תָּמִים, נָאִיבִי
The proper Hebrew word for naive is תָּמִים 
listen and repeat, as appears in Danny Sanderson’s זֶה הַכֹּל בִּשְׁבִילֵךְ listen and repeat – This Is All for You:
listen and repeat, as appears in Danny Sanderson’s זֶה הַכֹּל בִּשְׁבִילֵךְ listen and repeat – This Is All for You:אוֹ, דּוֹן קִישׁוֹט, אַל תִּהְיֶה כָּל כָּךְ תָּמִים.
Oh, Don Quixote, don’t be so naive.
But since this word has also been carrying the meanings of simple and perfect since its appearance in Biblical Hebrew, Modern Hebrew speakers tend to prefer the less ambiguous – albeit foreign – נָאִיבִי listen and repeat to describe a male and נָאִיבִית listen and repeat to describe a female.
listen and repeat to describe a male and נָאִיבִית listen and repeat to describe a female.For example:
הִיא מְבִינָה עִנְיָן – מִסְתַּבֵּר שֶׁהִיא לֹא כָּל כָּךְ נָאִיבִית.
She understands things – it turns out that she isn’t so naive.