Hello I have passed 11th and I am in 12th commerce with maths, I am passionate about engineering, should I repeat class 11 with PCM and prepare for JEE or should I take diploma after 12th? how much time will it take for diploma after 12th(5 or 6years?)my dream college is DTU(I am delhite).

You can go for diploma . Because after diploma you can go for b.tech and you can't repeat your class 11th again.
Atfast complete diploma then you can give lateral entrance exam

DTU can accept lateral entry .
The official website of college https://cumsdtu.in/AdmissionsWebsite/

https://school.careers360.com/articles/courses-after-10th


You can also visit here  for diploma

https://engineering.careers360.com/articles/diploma-in-engineering

You can visit the college names
https://www.careers360.com/courses

After diploma you can go for b.tech
https://engineering.careers360.com/articles/what-btech-lateral-entry-eligibility

https://www.careers360.com/university/delhi-technological-university-delhi

Thank you. All the best. I hope this answer helps you.