5. Do I need to make a self-introduction to you first?
我需要首先做下自我介绍吗？
还能这样说：
May I introduce myself first?
Can I introduce me to you first?
谚语：
A bully is always a coward.
色厉内荏。

6. The strongest traits in my character are cheerfulness and friendliness.
我个性上最大的特点是乐观和友好。

7. Can you tell me why you reply to our advertisement?
你能告诉我为什么回复了我们的广告吗？
还能这样说：
Could you tell me the reason to reply to our advertisement?
Can you tell me the reason why you answer our advertisement?
应用解析：
reply in the affirmative 肯定地回答；
reply to a salutation 答礼

8. Do you have any working experience?
你有什么工作经验吗？
还能这样说：
Have you had any working experience?
Do you have any experience on work?
谚语：
A woman's work is never done.
妇女的家务永远干不完。