slender man, real or fake?

No.

Slenderman is said to have originated as a German 'old wife's tale,' which gained popularity through internet users a couple of years ago (in the form of youtube series and blogs). The popularity of the phenomenon largely had to do with the fame of boogieman, before slenderman's arrival into the imagination of internet users.
It is likely that that the idea of slenderman was prevalent in societies well before the Germans, and may have been the same concept as the boogieman. The prospect of a very tall, gaunt man arriving from the dark scary forest, possibly with multiple limbs (depending on who tells the story), and with an affinity to abduct its victim and kill it gruesomely is enough to make any sane child frightened and drop their ill-mannered behavior at once. The tales of this figure may vary culture to culture, but it is a superstitious concept with universal appeal.
What you should get out of that long winded reply is that it is simply a figment of imagination.

but if we look close we may find more than ratinal thinking can, what hapened when Placebo introduced his "medical treatment" it was phenominal the amount of people who agreed to his treatment. In acordence to that i believe that a figment can become a fragment then compose itself into reality, but this is all just the beginning of profound thinking, Thank you for the information and i would like to hear more!