As all 4 wheels had these lines on them in multiple places and I dont own any alloy polish / a polishing machine, I decided to take it to where the work was done.
Turns out that the issue was something on top of the paint / laquer as polish did take it out (with the machine and a lot of elbow grease). Took over an hour in total but the guys at alloywheelexchange were very good and didnt charge me anything (despite the owner grumbling at me that they do not work for free).
All clean now so Im happy

but they didnt believe it was the locktite they use on the wheel bolts (as the colour of that is blue and the colour of the lines was black). So what it was is a mystery and I will likely have to invest in some polish either way ..