Hi Albina,
Thanks for your interest in Ziva = )
Time Warp is made for animation
Ziva is a simulation
To slow down or speed up your simulation use Frame Rate attribute on zSolver node
By default it's 24, you can decrease it to 12 to make it 2 times faster or increase it to 48 to make it 2 times slower
Also I would recommend to stretch your animation accordingly
Looking forward to see your results !