There will always be cases where an attack was prevented by someone carrying a gun, the reality is more guns in circulation = more gun homicides and more homicides in general as well as more mass shootings, as you can see in the US and even countries like Australia before the implemented the ban on guns.
Now imagine if that guy who committed the knife attack in Germany had bought a gun instead for the attack? We probably would be talking about a lot more than 3 dead people.
By the way, you do have considerably more homicides by firearms. More than 4 by 100,000 inhabitants while in countries like Germany it's 0.065.
Also: "2021
A little above 80% of all murders (20,958 out of 26,031) in the United States in 2021 involved a firearm— the highest percentage since at least 1968, the earliest year for which the CDC has online records."
Source:
https://en.wikipedia.org/wiki/Gun_violence_in_the_United_States
The best argument you have is that you love guns. Don't try to tell me guns would have saved those 3 people who got killed by knife. The death toll would probably have been a lot higher if guns were allowed in Germany, just look at the results of your mass shootings in the US. And by the way, most of those mass shooters don't get killed by someone carrying a gun until they've already killed several people.