Understanding sell transaction

Beginner Questions
1

Please help me understand sell transaction.

So far my logic thinking described below

I open a new account in UK pounds

first trade I do is sell EUR/GBP.

As a example the rate is

(bid price/ask price)
0.83818 / 0.83837

Seeing a description of bid and ask

Bid price: You can sell 1 Euro for £0.83818
Ask price: You can buy 1 Euro for £0.83837

So it seems I am paying £0.83818 in pounds for something but what exactly?
I dont have any euro yet i am selling euros?

I am not gaining pounds because I am paying in pounds?

It doesnt seem to fit the travel abroad analogy that is often explained because when
you go abroad and back changing between currencies each time its always a swap you get one for the other

2

You open your Margin Account in GBP.
You choose to short (sell) the EUR/GBP. (ie. You are simultaneously selling EUR and buying GBP).
Before your trade is executed your broker will automatically convert the required amount of GBP funds into EUR (hypothetically). They don’t literally do this.
As your trade is executed, newly obtained EUR are sold and you simultaneously purchase GBP in return.
If the trade goes in your favour (the pair fall in price), your profit will be in EUR.
Your profit or loss within the active trade will be in EUR.
You exit your trade (take a buy position as you took a sell position to open the trade initially) by utilising either a Take Profit/Stop Loss or At Market price order (via your existing active trade) and will profit or lose in EUR.
As your Margin Account is in GBP, your broker will automatically exchange your EUR profit to GBP based on the initial order price in the background and your Margin Account will go up or down depending on whether your trade was a win or loss.