all the font text in my check out page and success page turns white and also it becomes not visible

I HAVE TWO PROBLEMS THAT KEEP ME CRAZY FOR A WHILE NOW
FIRST ONE: all the font text in my check out page and success page turns white and also it becomes not visible because of the white background, i have tried editing the stylesheet.css of my theme but i keep getting same error, please i really need help on my store checkout page, please how can this be corrected to black, i really need this help urgent, thanks, i have some screen shot below...

SECOND ONE : the text on my check out title suddenly changed to SO FACEBOOK and writeup still not visible.. please help me

Hi there,

We should be able to help with this, would you be able to drop us an email to get an estimate?
info@antropy.co.uk

Kind regards,
Alex
www.antropy.co.uk

Hello,
I would be glad to assist you.
Please check your PM.
Thanks!
Anna

Hello,
Please check your PM and let me know. I have relevant experience in an Opencart and ready to help you.
Or you can email me at: info@elderberrytech.com to discuss further.

Thanks,
Shivank Agrawal
Skype: mayank.agrawal2008

Hi,
What you are wanting done is well within my skill set and I would be glad to help you out on this.
You can reach me on andrewjohnson56782@gmail.com
Best Wishes,
Andrew