Nuclear medium modifications of properties of kaons measured around threshold with FOPI

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.