Hi! I'm having some trouble with my playing. Now my tone has improved by working on my wrist and arm technique, as well as working on the different speeds that every string needs to produce the tone.. my problem now is that I can't get the dynamics of the music

I have no idea how to master the volume of the doublebass, how do you do to go from pianissimo to fortissimo and viceversa? Music is all about details on my opinion, and mastering volume is a very important topic when talking about details!!
any help will be appreciated