Solid Hardwood, Engineered and Laminate Flooring - Removal of Parkay wooden flooring

A few years ago I installed Parkay wooden flooring in my 1 bedroom apartment. The subfloor was not prepared for the installation and I have not been happy with the results. I never even finished installing molding as I knew it would be a matter of time before it had to be removed. I want to rip up the parkay flooring and have a professional come in and do new flooring. I figured I may save some money if I ripped up the flooring myself and prepared the concrete floor myself. I removed a 5 x 5 area to see the level of difficulty I would encounter and realized it would be manageable. It appears that there is up to three different layers of adhesive and/or leveling compound over the original concrete floor. I am not sure of my plan of attack. My goal is to remove the parkay and prepare the subfloor myself and then hire a professional to install new flooring. Or I wonder if I should just rip the old floor and let the professional prepare the subfloor and install the new flooring?

Explain what was wrong with the subfloor?

Do you own this apartment?

Second floor?

Answer those questions first, then we can proceed a bit further.

I will rarely trust someone elses floor prep, if I have to put my name on the installation.