7.9 CPI is certainly good for CSE first-year students at MNNIT Allahabad. It is tangible proof that you have decent knowledge about subjects such as Physics, Mathematics, and Chemistry. Having good knowledge of these basic science subjects will help you do well in the core CS subjects that you will study for 2nd years, such as Data Structure and Algorithms. You will also have the scope to improve your CGPA.
Grades are very important in our lives because they show how good you are in your studies.
Grades are extremely important if you want to pursue higher education, whether it's an MBA, an MS, or another post-graduate course. Some institutes will not even consider your application if you do not have the necessary academic credentials. In a broader sense, grades are critical if you want to pursue higher education.
So, the bottom line is that 7.9 is a good score, but it's not very good. Try to work on it. You still have plenty of time to improve your grades.