"be left home alone" or "be left alone in my house"? Which is more natural, "I was left home alone." or "I was left alone in my house."? Are there any differences between these sentences?

Sniff or blow your nose?

In Japan, it is more polite to sniff quietly than to blow your nose loudly in front of people.

But I hear that in other countries (especially in western countries), sniffing nose is hated and it is accepted to blow your nose with your handkerchief.

Is it true in your country? Which do you find it more polite, to sniff or blow your nose?

Do you use a handkerchief to blow your nose?

In Japan, people don't use their handkerchief when to blow their nose.

What do you do that makes you feel invincible? I found this question when I was studying English. I don't really understand what this question means. Could you give me some example answers?

I've joined an English conversation club! I've found an English conversation club in my town. People get together once a week and practice to talk in English! English conversation schools are very expensive, but the club is free! That's great! I'm going to join the gathering tomorrow for the first time. I'm really excited but a little bit nervous. But I must not be shy! I will talk a lot without worring about mistakes!!!

What can I say when a sales clerk says, "May I help you?" Some books says that you can say, "I'm just looking." Isn't it rude? Doesn't it sound strange when I have somethig I want to buy in my hand?