Complex sentence: The standard anti-tanks they had, the 3.7 cm Pak 36, did not have the penetrative power to stop the larger Soviet tanks, and the high mobility of the Soviet tank forces made it difficult to get the higher caliber weapons to where they were needed.
Split into simpler sentences: The standard anti-tanks they had, the 3.7 cm Pak 36, did not have the penetrative power to stop the larger Soviet tanks. Furthermore, the high mobility of the Soviet tank forces made it difficult to get the higher caliber weapons to where they were needed.