Unusable Android J5(6)

Hello all,

Some time ago a friend thought I would like to have his old Samsung Android
J5(6) phone.

The problem is that he didn't remove his credentials from the phone, and
now, after having booted, it effectivily refuses to function anymore - it
looks like it went into a 1980's speed mode, being super-slow and not really
responding to taps or physical buttons.

It does show a message about an attempted un-autorised reset (my attempt to
clean it up), wanting me to verify my friends identity.  The problem is that
my friend has no idea anymore what that was.

Question : is there still a possibility to get the phone back into a
functioning state, or has it become landfill material ?

Regards,
Rudy Wieser