  Context. Despite the fact that VW Cephei is one of the well-studied contact
binaries in the literature, there is no fully consistent model available that
can explain every observed property of this system.
  Aims. Our motivation is to obtain new spectra along with photometric
measurements, to analyze what kind of changes may have happened in the system
in the past two decades, and to propose new ideas for explaining them.
  Methods. For the period analysis we determined 10 new times of minima from
our light curves, and constructed a new O$-$C diagram of the system. Radial
velocities of the components were determined using the cross-correlation
technique. The light curves and radial velocities were modelled simultaneously
with the PHOEBE code. All observed spectra were compared to synthetic spectra
and equivalent widths of the H$\alpha$ line were measured on their differences.
  Results. We have re-determined the physical parameters of the system
according to our new light curve and spectral models. We confirm that the
primary component is more active than the secondary, and there is a correlation
between spottedness and the chromospheric activity. We propose that flip-flop
phenomenon occurring on the primary component could be a possible explanation
of the observed nature of the activity. To explain the period variation of VW
Cep, we test two previously suggested scenarios: presence of a fourth body in
the system, and the Applegate-mechanism caused by periodic magnetic activity.
We conclude that although none of these mechanisms can be ruled out entirely,
the available data suggest that mass transfer with a slowly decreasing rate
gives the most likely explanation for the period variation of VW Cep.
