100+ hrs work week with no days off - I will not promote

So i recently joined this early stage bootstrapped startup as a software engineering Intern where I am required to work around 14-15 hours a day , 7 days a week and they don't give weekends off.. essentially I'm like a robot working all the time -> sleeping and coming back. The founder just said this before joining so i thought the max will be 10 hours a day : "We enter at 10 am, And stay till war ends" I've done this for 3 weeks. There's 40 days left. I wanna quit but my friends are saying that i shouldn't