Hi Anika,
Have you been working with the auto key frame option turned on? It sounds like you made some changes and that got recorded as a keyframe and now as you go back and forth through the time line those key frames are changing your settings in the basic menu for that object. Is there a red dot beside the attributes that change? Anything other than a dull gray radio button means a key frame has been set somewhere in the time line.
The auto keyframe button (depending on your version of C4D) will be in the main timeline slider area near the play and next-frame buttons – it looks like two brackets inside a red circle (next to the skeleton key symbol) With that button turned on every change you make records a key frame.