Hey Jihan,
Sorry to hear about that
! A couple of poorer SAC marks does make it hard, and will probably affect your study score somewhat, but it's all about how you go from here. Together, the first 2 SACs make up 15% of your study score (plus they're then scaled by the exam), so you've still got the remaining 85% to change it!
So, if you want to pick up your marks in future, you've got to figure out where you went wrong. Then, you've got to keep asking questions and figuring out different ways of doing things, until you can fix that in the future. So if your issue is graphs and data (and that's probably not the only one), ask your teacher about how to fix it, or ask questions here on AN. I'll PM you about it actually.
There are lots of tips in the HHD board - you could look at
this post, plus
[50 in HHD] Health & Human Development in 2015 and beyond and
Guide to HHD (which has some tips about memorising content if you scroll down). If you've got any specific questions - like how to deal with data or answer certain types of questions - feel free to ask them in the
HHD [3/4] Questions Thread!
If you're willing to do the work and try to sort out where you went wrong, I promise you can pull up your scores
All the best!