I looked into moving from economics to actuarial. Go for it, your grades are fine. If you do Math & Stats you'll be overwhelmed with theoretical stuff in 3rd year. But actuarial is useful and practical, and pays very very well.
Improving grades in math requires this:
1. go to all the classes and tutorials, taking notes
2. do all the questions in the textbook
Improving grades in other courses requires going to all classes, taking notes, reading the entire textbook and taking notes, understanding and remembering everything, doing all the assignments, and leaving sufficient time to do everything. Sometimes you can't get better than a 9 no matter what you do, but other times this gets you an easy 12.
If you want to go through an exercise to improve your marks, this is what I learned years ago:
1. Print out, or buy from the bookstore, a daily/hourly planner.
2. In your first week, just take note of what you are doing every hour of every day for that one week.
3. At the end of the week, go through that planner and look at how you've spent your time that week. Ask yourself why you needed to spend 10 hours playing Minecraft/posting about your feelings on tumblr/whatever else the kids of today do.
4. For the coming week, schedule 2 hours of studying per hour of lecture time for each class you have into your hourly planner. Yes, that means something like 30 hours of studying a week. You can delete everything else in your daily life that doesn't help you get an education. You're not paying $7000 tuition a year to play Minecraft.
5. Follow your schedule. Always note a week or two ahead what is due.
6. Sleep at least 8 hours a day and eat nutritious food.