5. When can I have a double eyelid operation?
我什么时候可以做割双眼皮的手术？
还能这样说：
What is the right time for me to have a double eyelid operation?
What is the time for me to have a double eyelid operation?
应用解析：
double or quits double 要么加倍付钱，要么全部勾销；
double as （演员）兼演（另一角色）；
double back 向后折；把……对折；往回跑
6. Is the operation to make dimples on my face safe?
在我脸上做造酒窝手术安全吗？
还能这样说：
Is it safe to make dimples on my face?
I doubt the security of making dimples on my face.
应用解析：
come into operation 开始工作；生效实施，实行；
undergo an operation 接受手术
7. Can you tell me the riskiness of doing this plastic surgery?
你能告诉我做这个整形手术的风险性有多大吗？
还能这样说：
How much are the risks to have plastic surgery?
Can you tell me how dangerous to do the plastic surgery?
应用解析：
at one's own risk 自担风险。
例如：If you go hiking on a rainy day, you have to do so at your own rsk.
如果你雨天徒步旅行的话，就要自担风险。
8. You'd better get rid of the idea of getting a plastic surgery.
你最好打消做整容手术的念头。
还能这样说：
I suggest that you had better drop the idea to have plastic surgery.
You had better put the idea of getting a plastic surgery out of your mind.
应用解析：
open-heart surgery 体外循环心脏手术；
plastic surgery 整形外科；
spare-part surgery 器官移植外科