I tried to smooth it by pressing Shift and smoothing, and tried smoothing it with the Smooth option in sculpting. But nothing seems to work... does anyone know how to help?
You need to retopologize your mesh in Blender, that is the only option, the smooth brush is unable to deal with this.
These artifacts are caused by triangle fans, usually left from dynamic topology, and are impossible to smooth perfectly, because the smooth brush in Blender is not actually a smooth brush but averaging brush. If you can import this into Zbrush, there you will be able to comfortably smooth this without retopology with the alternative smoothing mode, but not in Blender.
For retopology you can use the Remesh modifier on a copy mesh, that you Shrinkwrap to the original, subdivide evenly, smooth and you continue sculpting.