Good morning sir, Torsten
The point I like to rise here it is about the “pronunciation”. As a no native English speaks I experienced that although I speak English fluency but some words it makes me difficult to pronounce. My tongue cannot turn properly. Is it anything else that may unlock this mechanism? thank you.
All the best,
Robert
Hi,
I’m not Torsten 
but I’ll be happy to give you some advice.
Improving one’s accent is almost always a matter of getting the correct tongue/lip position for every vowel/consonant, and furthermore it’s a matter of linking words and getting the right pitch/rythm. There’s a lot of work involved in learning/aquiring an accent, and there’s no shortcut. You must do a lot of drill work to drill sounds into muscle memory to get any improvement.
I myself use this resource on the internet (it’s free and there’s oddles of useful information): WWW.RachelsEnglish.com
It suits me to a t, but of course feel free to use something else, if it helps you.
Also, there’s a recoding facility on this site, which allows you to record your voice and post it, together with your text message. So use it too, to get better.
Also, you need to get in the habit of speaking English for at least 10-20 minutes on a daily basis to expect a steady improvement.