Can someone please explain what is happening in the predecessor function of Church numerals. Step by Step please!

pred: nfx.n(gh.h(gf ))(u.x)(u.u)

pred one

==> (nfx.n(gh.h(gf))(u.x)(u.u))(fx.fx)

==> (fx.(fx.fx)(gh.h(gf)))(u.x)(u.u)

==>(fx.(x.(gh.h(gf))x))(u.x)(u.u)

==> (fx.(x.h.h(xf)))(u.x)(u.u)

==>(fx.(h.h((u.x)f)))(u.u)

==> (fx.(h.hx))(u.u)

==>fx.(u.u)x

==> fx.x

==> zero