You improve your grades moving forward by addressing the cause(s) of the poorer than desired 9th grade grades. For example, if you did poorly first semester because you failed to turn in assignments, perhaps you need to note any assignments and due dates in a planner before you leave class. Then when you get home, break long-term assignments into weekly segments. Add those self-imposed deadlines to your planner. As you complete each assignment (or segment), put it in your class folder. Make sure all class folders are in your school bag each evening before you go to bed. That way you will have them when you get to class.
On the other hand, if you have always excelled in the past and now have struggle to master the materials, work on study skills. You need to study smarter not necessarily longer or harder. One way to study smarter is to ask for help as soon as you realize you are struggling. Many schools offer peer tutoring. That is a good place to start. If no peer tutors are available ask your teacher for help.
Algebra 2, honors or not, is advanced for 9th grade. What math will you be taking in 10th? I suggest you spend some time this summer using Khan Academy to review. Do the diagnostic tests for Algebra 1 and work your way up.
If you cannot handle schoolwork plus an extracurricular activity or two, either you are taking coursework that is too advanced for you or you have poor time management skills. If the former, it is better to take regular-level high school coursework and have a few activities you enjoy than to do poorly in advanced courses because you took them too soon. If the later, work on that this summer.