  We present ALMA observations and multiwavelength spectral energy distribution
(SED) analysis in a WISE-selected, hyperluminous dust-obscured quasar
W0533-3401 at $z=2.9$. We derive its physical properties of each component,
such as molecular gas, stars, dust and the central supermassive black hole
(SMBH). Both the dust continuum at 3 mm and the CO(3-2) line are detected. The
derived molecular gas mass $M_{\rm gas}=8.4\times10^{10}\ M_\odot$ and its
fraction $f_{\rm gas}=0.7$ suggest that W0533-3401 is gas-rich. The star
formation rate (SFR) has been estimated to be $\sim3000-7000\ M_\odot$
yr$^{-1}$ by using different methods. The high values of SFR and specific SFR
suggest that W0533-3401 is a maximum-starburst. The corresponding gas depletion
timescales are very short ($t_{\rm depl}\sim12-28$ Myr). The CO(3-2) emission
line is marginally resolved and has a velocity gradient, which is possibly due
to a rotating gas disk, gas outflow or merger. Finally, we infer the black hole
mass growth rate of W0533-3401 (${\dot{M}}_{\rm BH}$ = 49 $M_\odot$ yr$^{-1}$),
which suggests a rapid growth of the central SMBH. The observed black hole to
stellar mass ratio $M_{\rm BH}/M_\star$ of W0533-3401, which is dependent on
the adopted Eddington ratio, is over one order of magnitude higher than the
local value, and is evolving towards the evolutionary trend of unobscured
quasars. Our results are consistent with the scenario that \wobs, with both a
gas-rich maximum-starburst and a rapid black hole growth, is experiencing a
short transition phase towards an unobscured quasar.
