How many dimensions and universes do we actually have?

This depends greatly on the observers perspective. Viewed in the macro scale from a fixed observer perspective we see a flat, unified, single universe with dimensions expressed in definable quantities. However when viewed from the super-micro "quantum" perspective these terms cease to have meaning as universes and dimensions become infinite and therefor un-quantifiable. As we are only able to model the macro perspective from a human understanding the quantum reality remains accessible only in the imaginary.