Account does not exist any more

Hello there!
I don’t know if im posting at the correct section.Please forgive me.

Here is the question :
Many months ago, there was a guy in the company i am working now and he created a website with wordpress (version 3.4.2) while the latest stable version right now is 4.0.1.

That means that it is required to update the version. But in order to update the wordpress version, im trying to log in through browser https://www.motive-consulting.gr/wp-admin.

Here is the problem that i have to deal with:
Even if im trying to log in with username and password i can’t because there is a message “Invalid username”. After this i press on “Lost your password” and i put an email but unfortunately that email does not exist anymore. The guy who created the website,has left the company about a year ago and now i have to update the version. Everyone here at the company has a new email (something like [email protected]) and since he left, that email has been deleted. The companys website was created on that email. And now it doesn’t exist anymore.

So here is what kind of help im trying to ask from you guys.
Can you allow me to put an other email as main email and change the password so i could work finaly on that bloody update? ??

Thanks in advance