At least two things were finished

Something is such that (it was finished and something other than it was also finished)

∃x (Fx ∧ something other than x was finished)

∃x (Fx ∧ (∃y: ¬ y = x) Fy)

or
∃x (∃y: ¬ y = x) (Fx ∧ Fy)

Something is such that
something other than it is such that
(both of them were finished)

or
∃x ∃y (¬ y = x ∧ (Fx ∧ Fy))

Some pair of things is such that
(they are different
and both of them were finished)