Perhaps you are right. Like other old video games, this game is faster than it should be on modern systems. Fortunately, you can solve this problem by editing the DOSbox configuration file.

Configuration file is located at the following path:
Steam\steamapps\common\Across The Rhine\dosbox_windows\dosbox_atr.conf

Set "memsize" to 16, "core" to simple, and "computype" to pentium_slow. With these settings, the game will probably run at its native speed.