You modified my sample code a bit too much - you always set the animation at track index 1 instead of one animation at index 0, the other at index 1:
track0 = skeletonAnimation.AnimationState.SetAnimation(1, "rire", true);
track1 = skeletonAnimation.AnimationState.SetAnimation(1, "rire2", true);
It should instead be:
track0 = skeletonAnimation.AnimationState.SetAnimation(0, "rire", true);
track1 = skeletonAnimation.AnimationState.SetAnimation(1, "rire2", true);
Same applies to the block below.
Great to hear that it now works! I just wrote the posting a few minutes before you edited the posting above, so you can ignore it in the meantime.