Need admin access to new client site

Hi,

I’ve been contacted by a new client running a WP site that was developed by another company, now bankrupt, and founders are unreachable.
This client gave me his access to the admin, FTP, DB, and a brief of work to do.

Now his account is limited, I can’t create menus, etc. He has no other access and again the previous developer does not answer any communications and disappeared completely…

Is there a way to kindly “hack” the admin account ? Knowing I can access the DB, files by FTP, everything, and I have the authorization of my client who needs help, of course…

Weird request I guess, but I hope to find some help ??

Thanks in advance