It is possible to make a subject a breeze or a burden. It all depends on how you approach subjects. If you find any subject difficult you must change your approach to it. Make more time for the subject. Do more with the subject than you would in “standard textbooks”. Ask your teachers and anyone with a deep knowledge of the subject to clarify any doubts. You will begin to notice the changes slowly. It will all be easy. It won’t happen overnight. You may have to wait for weeks, or even months. But don’t lose heart. I will recommend Engineering Mathematics by Dr.B.S.Grewal, since you said mathematics is difficult for you. Microelectronic Circuits, Adel S Sedra, and Kenneth C Smith will assist you in understanding BJT biasing as well as other fundamental electronics topics. Change your attitude toward difficult subjects and learn with passion. That’s it!