Does anyone know how to make an animation system that uses Crossfade?

I want to make my weapon move when I walk but I want it to change animation as soon as it starts running, but the system I currently have waits for the animation to finish and then executes the other one. I also don’t want it to be a very abrupt change between animations

Go to your animator, click on your transition arrow, disable “has exit time”. Unity automatically crossfades between animations, which you can change in the animator window as well.