  We present an optical study of the strong lensing galaxy cluster MS
0440.5$+$0204 at $z=0.19593$, based on CFHT/MegaCam g', r'-photometry and
GMOS/Gemini and CFHT/MOS/SIS spectroscopy in a broader area compared to
previous works. We have determined new spectroscopic redshifts for the most
prominent gravitational arcs surrounding the central galaxy in the cluster. The
new redshifts and the information provided by the photometric catalog yield us
to perform a detailed weak and strong lensing mass reconstruction of the
cluster. The large number of member galaxies and the area covered by our
observations allow to estimate more accurately the velocity dispersion and mass
of cluster and examine in detail the nature of the cluster and surroundings
structures. The dynamical mass is in good agreement with the mass inferred from
the lensing analysis and X-ray estimates. About $\sim$68\% of the galaxies are
located in the inner $\lesssim$0.86 h$^{-1}_{70}$ Mpc region of the cluster.
The galaxy redshift distribution in the inner region of the cluster shows a
complex structure with at least three sub-structures along the line-of-sight.
Other sub-structures are also identified in the galaxy density map and in the
weak lensing mass map. The member galaxies in the North-East overdensity are
distributed in a filament between MS 0440.5$+$0204 and ZwCL 0441.1$+$0211
clusters, suggesting that these two structures might be connected. MS
0440$+$0204 appears to be dynamically active, with a cluster core that is
likely experiencing a merging process and with other nearby groups at projected
distances of $\lesssim$1 h$^{-1}_{70}$ Mpc that could be being accreted by the
cluster.
