So I grabbed some normal clothes from a wardrobe, put them on and unequipped all weapons and only put them on a hotkey pretending it would be like a hidden dagger under your clothes.
After some shopping in Falkreath I traveled to Windhelm to kill my first target: Ennodius Papius who lives at Anga′s Mill.
After getting there I talked to some of the workers but they only said that I have to talk to Aeri for work. Since I only had little money left and didnt want to be suspicious I took the offer and chopped some wood. While chopping some wood the other workers even talked about Ennodius Papius and how strange he was. After chopping the wood I got back to Aeri to get paid and after giving me the money she gave me a new job: delivering a note to the Jarl of Dawnstar.
After taking the offer I proceeded going the way up the hill to dawnstar but first I took a left turn to visit my target Ennodius Papius. His paranoia enabled him to see through my disguise but I swiftly took out my "hidden" dagger and stabbed him multiple times in the chest. After seeing his dead body on the ground in his own blood I continued my journey to Dawnstar to deliever the letter from Aeri and to do my dark work again and kill the mine boss Beitild.
So I hope you liked this short story of my assassin. After doing this kind of roleplay I must say that I never want to go back to "normal" playing. It was such a good experience.
And I can only recommend it to everyone because actually playing your role and living their life makes the game even more awesome than it already is.