Since you're from Germany, you probably have a PAL SNES. PAL was the TV standard that was used in most of Europe and Australia, so any SNESes sold in those regions are likely PAL as well. The standard in other regions was NTSC, which means SNESes sold there are NTSC systems.
The difference between PAL and NTSC is that PAL TVs run at 50 Hz, whereas NTSC TVs run at 60 Hz. In other words, PAL TVs will display 50 images a second, NTSC TVs will display 60 images.
An SNES always runs at the same frame rate as the TV it's meant to be connected to, this means a PAL SNES displays 50 frames per second and an NTSC SNES displays 60 frames per second. Since all SNES games that I'm aware of are actually timed based on their refresh rate, this means that games running on an NTSC SNES will be about 20% faster than the same games running on a PAL SNES.
Back in the days, developers often worked around this problem by making small adjustments to their games for PAL releases, making them play slightly faster on PAL systems to cancel out the system's slower refresh rate. That's why the speed of a lot of official PAL SNES games still feels "just about right" when played on a PAL SNES.
The problem with SMW hacks is that they're all based on the (US) NTSC version of SMW, so they don't include any of these PAL-specific adjustments. That means when played on a PAL SNES, they will actually run slower than their intended speed.
Basically, there's only a few ways around this problem.
-Play the game on an emulator
-Perform a hardware mod on your SNES, which will allow it to play games at 60 Hz
-Buy an American or (preferably) Japanese SNES, which will run at 60 Hz natively
Note that the last two solutions also require having a 60 Hz-compatible TV, but as far as I'm aware, pretty much any TV released in Germany in the last couple of decades should be 60 Hz-compatible.
--------------------Feel free to visit my website/blog - it's updated rarely, but it looks pretty cool!