本気で思ってるの

do you really think …?

→ 本気
phrase Rare #35,712
do you really think …? Often used as a skeptical or rhetorical question. 思ってる is a casual form of 思っている.
JA: 彼が一人で全部できると、本気で思ってるの?
EN: Do you really think he can do it all by himself?

夜通し運転しようだなんて、本気で思ってるの?

Do you really think you can drive all night?

トムは勝てるって、あなた本気で思ってるの?

Do you really think Tom can win?

トムが悪いとか、本気で思ってるの?

Do you really think Tom is to blame?

手を貸すとでも、本気で思ってるの?

Do you seriously think I'd lend you a hand?

いい年して、再婚しようとか本気で思ってるの?

At your age, do you really think you’re going to remarry?