The 'square of something on the bottom of the heatsink' pinky in colour is a cooling pad. These are not usually any good. Generally heatsinks that come with that stuff on them are not to be used on highend systems.
Get rid of that stuff by removing as much as you can with an impliment that will not scratch the base of the heatsink and then clean it thouroughly with Isopropyl alcohol. Then get some heatsink compound (several to choose from), I usually use Artic Silver 'ceramique' as it is non conductive and apply a thin layer over the cpu core. Then put the heatsink back on top.
For better cooling you should really buy a heatsink that is all copper with at least an 80mm fan. A high quality heatsink will not have any paste whatsoever on the base.
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