See for most of the diploma course the time period for completing the course is 5 years. For example if you are admitted in 2020 to the 1st year of Diploma then your course must end on 2023 but if you can't complete then you have to complete the course with in 2025 to get the diploma on the same basis of registration. So if you have the 5 years period from your admission then you should contact your college and get it discussed, they will guide you out.

To know more about the career in Diploma in Civil Engineering visit the link below:

https://www.careers360.com/courses/diploma-in-civil-engineering

I hope this answer helps. All the very best for your future endeavors!