Thanks.

«In the Electrum desktop wallet their will be lot of address and even if you receive bitcoins in different address but when you are sending the coins it will send from all the address to one single transaction if you are doing all out»

Yes, this I understand, but as I will not bring my desktop to the ATM, it will not send anything, except some of its asset, if possible, transferred to a mobile (phone) app.

So I think that the question
1- Should I download Electrum for Android on my mobile phone?
is yes, or with blockchain.info app suggested by leonair, or, other suggestion here?

On the question
2- On Electrum for Android, (or other phone app)

Option A- do I create a wallet with my Electrum desktop seed and have everything (3 address), or
Option B- do I create a new wallet?
I think the answer is Option B, as also suggested by leonair.
Which makes sense. If I have 10,000$ controlled by my Electrum desktop wallet, I would prefer to have 100$ controlled by my mobile app to cash 75$ at the ATM.

«if you do part then...»

This, I understand as being the sweep process and we arrive at my question
3- Do I sweep 2 address from my desktop to 1 address on my mobile.
Please, explain the process of sweeping.
Is it my Electrum desktop that begins the sweep process or the Electrum mobile?
Do I have to sweep all the address or, what I would like, only 2?
And can we sweep the 2 address at the same time?

Can someone explain this process?

Is it the Electrum desktop wallet that sweep a part, in my example 2 address of 50$ each, to a BTC phone app, or,
is it the BTC phone app that asks some address (here 2) to be swept from the Electrum desktop wallet?