Need help styling Register form and Payment Screen, ive tried but am stuck

Hello,

You can see here https://seoinerg.com/registro and here https://www.mindfulscience.es/suscripciones/ I have styled these forms. But I am having trouble getting the grey background to remove and still appear around the account info fields..

What I am trying to do is get these forms to look like they do from this site here

https://restrictcontentpro.com/checkout/

mainly separation of the Payment Selection, personal info and Credit card info..

can you give me any suggestions on this?

Thanks in advance

EJ