Can you answe Riddles?!

Hi everybody
Riddles are a kind of entertainment for our brain. Some of them are very easy and the others are complex and need more intelligence and intention to understand the meaning.
In my opinion, they can also be used to enrich our knowledge and vocabulary as regards training languages.
Thereby, to stimulate your brain I propose these easy riddles:

We put me on the table.
We cut me, but we don’t eat me.
whom am I ?

I’m as big as the Eiffel Tower and lighter too.
Whom am I ?

You can have me but cannot hold me; Gain me and quickly lose me. If treated with care I can be great, And if betrayed I will break. What am I?

Almost everyone needs it, asks for it, gives it, but almost nobody takes it. What is it?

What never asks questions but must always be answered?.. The telephone

I’m not sure, but could the answers be:

  1. Appetite?

  2. (A column of) smoke?

  3. Friendship?

  4. Advice?