The PANDA experiment will be built at the FAIR facility to perform high precision tests of the strong interaction through $\bar{p}p$ and $\bar{p}$-A annihilations. To track charge particles, PANDA uses two straw tube trackers : cylindrical Central Tracker and planar Forward Tracker. The PANDA straws consist of very thin (27 $\mu$m) aluminized-mylar foil and are self-supporting thanks to the application of 1 bar over-pressure of the working gas. The straws will work at very high particle fluxes reaching up to 20 kHz/cm$^2$. We have studied gas gain drop due to the space charge produced at high rates. For this we irradiated the straws with X-rays from a strong Fe-55 source. For the studies we used a prototype straw tube module for the PANDA Forward Tracker. We have also measured electronic cross-talk between neighbouring straws in the module. Details of the applied experimental method and obtained results will be presented.