If you find Mathematics difficult then, Please don't assume that You can not learn it and also remember that you can learn everything. You need to be patience  I find myself to be perfect to answer this query because when I was in class 9th I was very weak student of Mathematics but Later I scored more than 90 in 12th. 

You need to start from basic Topics such as Relation and function they are easy to understand solve sufficient Problems and then switch to AP GP and quadratics equation. First, you read some topic and later start solving easy questions, don't look for a solution even if you can not solve it after a lot of attempts, again go and read the concept and try again. Biggest mistake while learning Mathematics is looking for solutions without solving the problems. You need high levels of concentration while solving Problems. If you don't find interest yourself Interested in Mathematics then read the book 50 Challenging problems in Mathematics  If you read it You will create a lot of Interest in Mathematics. If you are having computer Science as a subject then solve Problems you will find Mathematics useful there.

Dear Aspirant

Even though score of 11th class is not important, but the syllabus of 11th is very important for the exams that you will be giving after your 12th.

There is a sudden change after 10th std to 11th where many students find it alot difficult. 

But you need to understand that this time wont come back. You should first analyse the syllabus and there are few chapters that are quite easy in it. 

You can refer some online support, youtube tutorials or seek out your teacher or a friend at any time. 

All the Best, Believe in yourself, You can do it.