I dont understand 12th science what i will do
Hello Akash,
It's okay if you don't understand 12th science, not all of us can. It will take lots of practice and hardwork in the beginning. However, if you still are unsure about science, take another stream. If you already have chosen a stream, some schools do offer change of streams within one to two months of starting of classes. There are countless opportunities for non science students also.
Hope this helps.