To begin with the dingbat that had it before you should have known you
never put a finished floor on a slab without sleepers in between. And
a leveler has to be put on a bare surface. NEVER NEVER NEVER put vynal
on vynal. Or for that matter carpeting or any pliable surface on
another pliable surface. A breathing surface must have a hard
underlayment beneath it. Heat and elbow grease is your only solution.
That and LOTS of time. I don't envy you.