After you book
What happens once payment goes through, and how to check a booking is real.
The confirmation page
After you pay you land back on Arvald, on a page for that booking. It says whether the payment went through.
It can say pending for a few seconds. That is normal: the payment processor tells Arvald the payment succeeded a moment after you see it succeed, and the page waits for that rather than guessing. Leave it open and it updates itself.
Arvald does not email you about bookings
Worth stating plainly, because most things that take a payment do. No confirmation email is sent, and no reminder before the session. If you want a record, keep the confirmation page open, save its link, or sign in and use your bookings list, which is the place this is actually solved.
The one email Arvald sends is the six-digit code you use to sign in.
Your coach sees the booking on their side as soon as the payment goes through, so nothing is waiting on you telling them.
Keeping the link
The confirmation page has its own address, and anybody with that link can see that booking. It is not guessable, so it is safe to keep, and worth not forwarding.