this has been solved now
Hello,
$\displaystyle \Delta S=n \cdot R \cdot \ln \left(\frac{V_2}{V_1}\right)$
If $\displaystyle V_2 < V_1$ then $\displaystyle \frac{V_2}{V_1} < 1$ and then $\displaystyle \ln \left(\frac{V_2}{V_1}\right)<0$ that means negative and therefore the complete product is negative too. Thus $\displaystyle \Delta S$ is negative so there is a decrease in the entropy of the gas.