I bought me the Scrivener program like Sachinwalia sugested - it has an option to create the .mobi-format that is used by kindle, so that I can view it on my Mac before the upload. That solves my problem

- so thank you again for your tipp!
No I hope that the Index-function still works after the upload ... I create an Index by making it in Word and then exporting the text including the index to Scrivener. Nothing else worked before.