1. How can i disable the game from switching to the next ship, after my current ship has depleted its movement points
Try the option "Skip Moves Left Over From Auto Pilot". Its mentioned in the manual (english version) on page 21. It should prevent the game from moving on the next ship, even if it has moves left over.
If not, I'm not sure what you can do. You might have to look for the expansions for this option.
2. How can i change my german version into the english one? Since all videos and voice-overs are in english and even some text is still in english, i would like to change the language files (if there are some) into the english version, so all text and menus are now in english.
Try e-mailing stardock support. They might be able to assist.
5. Are there any topics here which describe how to create good colonies and how to come to a good income? My colonies are almost useless if i want money. The trading routes are much more profitable, while the colonies should be the heart of every empire imo.
Make many economy worlds. 1 farm, 1 morale building, a pair of factories, and a bunch of stock markets. Once you have enough income, you should be able to support a few factory worlds and research worlds (don't forget to use the manufacturing capital, and research capital).
6. How can i create basic ship designs which are shown on every techlevel? The custom ships disappear whenever i start a level again, but i would like to use at least the design again.
Templates were added in DA expansion as a means to solve this problem. Any template ship you make will have all the jewelery you gave it, but none of the weapons and other components that require techs to build (save for the hull size). You could select this template ship for the templates tab, and then upgrade as though it were a normal ship.
However, this option does not exist in DL version. You're going have to make your templates as though they were normal ships, but without any functional components that might add a required tech to list of prerequisites to build (beyond the required hull size tech). Try calling it "something template", and work from there.
7. Is there a way how i can upgrade an existing ship design, without having to place all things again? e.g. i have researched a new laser and want to change the ship design to use the new one, but i always have to place all engines, life support, sensors and other stuff again.
There might be an option that strips a ship of all functional components. You will probally need to turn this option off if you want to keep all functional components when you upgrade. In turn, you will have to manually remove all unwanted components (which I assume you are fine with).
8. For what are trading goods like Nano-Recorder good for? Only to trade with another empire and giving them this commodity one time only for ridiculous 200MC, while the building itself has cost thousands of MC?
Some trade goods are quite powerful. Many of them are worth getting as a means of making yourself more powerful, while denying your enemies the said advantage. They work better than techs in this regards as your allies can't trade these goods away like they can with techs, and these bonuses can't be stolen like you can steal techs. However, you have to watch out for enemies capturing the planet it was built on, otherwise they gain the advantage and can trade it to others.
I hope this helps.