Have you been using/have Android Pay?
Google merged Android Pay into Google Pay a month ago.
Seems its probably just an update rather than anything hacked.
I'm not sure where you're seeing 'device administrator' but Google pay would need to be to control the NFC etc.
If what you said was true, you would remove your credit card from google play. Also, probably make sure that you don't have a bank that uses your curent phone as a two factor authentication. Also, change your Facebook and email accounts to some other phone.
As I was typing a question into the google search bar the administrator was deleting it saying they didn't give permission for me to ask that question. It showed in the Google search history. Should have taken a screenshot. I just deleted it. I had to disable google play services to take the administrators off my phone but then gmail and play store didn't work. I enabled it yesterday to use email and the administrators are back. Seems to me I shouldn't be using PayPal or checking my bank balance on this phone if google pay is in charge of my phone unless there is some other explanation for all of this. I don't have a credit card ams have never used google pay before. Find my device is the other administrator. Apparently they can lock my phone whenever they want
Yes, a screenshot of something would be nice, since you aren't making sense. Sounds more like someone has remote control of your phone and is playing pranks on you. If you don't value what's on the phone, you can go into settings and do a factory reset. Like getting the phone new, so make sure you got all your snaps off it.