Thanks everybody for your help...
I don't know how fanfics were built at all, I'm sorry.
When I put the 3 books in the Kobo, there were about 80 books already in it... I don't know if it's considered like much or not
Anyway it is a good idea, I will wait more time the next time I will have to put new books in it.
I know that it is not my USB Cable but I wouldn't swear that my usb ports are innocent in my case
So I plan to try with another computer...
When I will have the courage to do this, I will up my post with the results
Thanks for your patience everybody...