Hi reijam,
All mattresses will go through an initial break in period over the course of the first few weeks and your body will also go through an adjustment period with any new sleeping surface over the first few weeks as well.
As you probably know from your research here … what feels firm or soft for different people can vary widely but there is more information and suggestions about a new mattress that is firmer than you expected in post #2 here that may be helpful as well.
Phoenix