I just found the library Williamchart https://android-arsenal.com/details/1/769.
There are many different Easings to animate the graph... I think... https://github.com/diogobernardino/WilliamChart/wiki/(7)-Animation
It has really cool animations to bring the graphs in front. But: how? Has anybody a usefull example how to bring a line chart as cool as on the website I linked to the front?