Ok I think I found a solution for it. So for people also having the same problem:
First select the material and go to "diffuse"
Then search in the options for the texture after "plugins"
from there: >"corona">"UVW Randomiser"
When chosen, (still in diffuse) you can click the little texture Icon and change the offset, scale rotation, etc...
For me this worked fine, but if there is a better solution, feel free to comment;)