Hi ctipz,
Post #2 here and post #2 here may be worth reading and I would certainly give things at least a month. Your mattress has mid density memory foam which is usually less “stiff” than higher density memory foam and your layers are also fairly thick so it may just need to go through an initial break in period and you may also need some adjustment period to get used to a new mattress.
This may be particularly true if your mattress seems different from the one in the store that you tested which would likely have broken in already.
Phoenix