  We report on the investigation of modifications of basic properties of K$^+$
and K$^-$ mesons emitted from collisions of Ni+Ni at beam energy of 1.91A GeV.
Experimental K$^-$/K$^+$ ratio are presented in a wide range of phase space
parameterized by kinetic energy and emission angle in the nucleon-nucleon
centre of mass. The $v_1$ component of the azimuthal distribution was extracted
as a function of rapidity and transverse momentum for central, and
semi-peripheral collisions. A comparison of these patterns with the HSD
transport model favours the existence of the kaon-nucleon in-medium potential.
For the IQMD model, this interaction scenario is confirmed in case of K$^-$,
whereas for K$^+$ the picture is less clear.
