still I cannot get rid of the influence of my mother language.
That does not sound like a worthwhile goal. :-)
In this modern world, all English is influenced by our unique cultures. It's better to let your English be unique.
However, I recommend Stephen King and Ernest Hemingway.. because they both have a simple, powerful style. I do not recommend a simple style because of some idea that you cannot handle complexity. I recommend it because simplicity is power in communication. When people write formal pieces or when they are practicing English they too often make language unnecessarily complex. They think complexity is impressive, but it's not. It is impressive to be able to understand complex pieces of writing, but when you write it should be straightforward and simple.
Thanks for practicing with us here. :-)