How to scrap a car properly or transfer to a motor trader

Hello everyone, this question has probably been asked many times, and apologise for this but since I find myself in a completely new situation and it’s my first time, and I don’t have anyone who can help me (I live alone and my family does not live in this country) apart from the gov.uk website, it would be great if you could give me a hand especially to ease my anxiety about not doing things correctly and ending up facing unpleasant consequences.

I contacted a scrapyard (an Authorised ATF) to take a car that I am scrapping.
They said I can bring the car at any time and they will give me £150.

I checked the gov.uk website to make sure I had all the necessary information.
The website says to give the V5C to the ATF and to keep the yellow section with me (so I assume I need to detach it from the V5C)

I do not really know if they keep the car or destroy and to be fair this is not really an issue as soon I am not the keeper of the car anymore..

Then, I have to notify immediately to DVLA (though online) that the ownership has been transferred.

This is what is making me a bit anxious.
When should I complete this step? Once I get home, or directly there on the spot online using my smartphone?

I’m worried about arriving there and being overwhelmed with information (my English is okay, but when people speak very fast I struggle) and getting confused.

Could you please help me by explaining the process and what would be best to do?

Many times it seems easy and straightforward, but lately I’ve been struggling a bit with anxiety and I’d like to avoid unnecessary overthinking.

Thank you very much.