There wasn't any solution book for that book! If you are studying on own, I will suggest you two things

1. It seems you currently have 8 or 20 months left depending on if you are in 11th/12th. Ànyways Its a much time! Try to do as many questions from your own, or by the help of examples! Ask questions you don't know from any good teacher in your area !! But I think That is what where the problem exists. So
2. There's are Author named A. Dasgupta & ML khanna ..Purchase Mathematics book of these authors. Most problems in SK Goyal have solved problems in these !! Kota coaching also has a number of problems from these in DPP