Usually, you cannot change from a business to a personal account.
You can ask Ebay if they will do this, but other members have said that when they have asked, it has been refused.
The best way forward is to close this account and simply open a new private account.
Use the link to contact Ebay Customer Services and see what they say,
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)