Believe me, you can!
For most of the students, class 11 is like a transition phase after the class 10 board exams. There is no pressure of studies, we study when we want without caring much for the scores and end up messing everything. At least I did!
But the important thing here is not to judge yourself by your class 11 performance. One year of dedicated studies is more than enough for a good percentage. Just make sure you have everything properly planned out. Be it the initial first study, or the final revision. Keep revising everything and try to score good in the pre board exams as well. Also listen to the teachers and try to remain attentive in class (yes, I’m not joking!).
Thoroughly practice the NCERT’s. Everything they ask is from the ncert’s only. Cram up the portion which needs cramming. Do not leave anything for the last (I did a similar mistake in my chemistry paper and left the last topic ‘Chemistry in everyday life’ to learn during the boards. I never touched that!). If you have maths you may solve other books like R.D. Sharma, but make sure you have practised the ncert’s fully.