New Email Set-up, Authentication using DKIM

I've decided to go with a different domain for my new website: holdbacktime.com.
I've owned this domain for years and used it for my first business. But, I think it needs fully authenticating. I bought it from Fasthosts.

I also want to have holdbacktime.com email in G-Suite. Can we make tinaaribib.com ‘dormant’ and replace it with holdbacktime.com? Because if you delete tinaarbib.com wouldn’t I lose my associated docs? And I don't want to be paying for 2 accounts. I would like tina@ and hello@ for holdbacktime email.

Hope this makes sense?

Do you have some time to do this work for me?

Kind regards,

Tina Wyatt