Hi Antoni,
thank you so much!!
What i think i have learned:
animation=openfig('animation.fig'); % not only just opening but defining an 'object' being the actual parent
NAxes=animation.Children; % here i learnend about correct use of children/ parent settings
a1=NAxes(1); % within NAxes() are all 'children' of the current parent figure. Might be static text, axes...
plot(YourData,'Parent',a1) % Plot/ write data in current parent and in children a1 as declared the line above
Heiko :)