hi,

see b.tech course is of 4 years duration, with 8 semester. in every year there would be two semester exams with practicals. however if you have low score in one semester do not need to loose hope, study hard for next semester exams, your final cgpa would be count by calculating  the average marks of all semesters. focus on the areas in which you have difficulty, contact with faculty members and also look for online study materials for better understanding .