Don't know what you mean by EFI-Boot-Mode. Do you mean you get a bunch of white text on a black screen? If so, that's Single User Mode. And if it's doing that, I'm surprised the shop gave your Mac back to you that way.
Turn the Mac off and then back on. Immediately hold down the Command+Option+P+R keys. Keep holding them through three startup chimes. Then let go and allow the Mac to startup normally. Does it boot to the desktop now?
Thank you, Kurt.
You're right, the Mac was starting in Single User Mode, and erasing the P-RAM has fixed that issue. The guy at Apple help desk couldn't give me that information.
But still there is no serial number. I think, this was a #*?:;/&%-repair of my reseller! I have to send it back for accomplish it.
Having the serial number disappear is not at all unusual when a system board, and sometimes even when just the original hard drive is replaced. I wouldn't send it back just for that.
There's really nothing wrong with it to be that way, other than making it slightly harder for you. Like when you call AppleCare. The first thing they ask for is the serial number, which tells them exactly what model Mac you're calling about.
But anyway, it's not completely gone. The serial number is on the MacBook Pro in a few places. And as the page mentions at the bottom, it will also be on your purchase invoice for the Mac.