For example: if i use bound burning head and my opponent has the normal burning head in his list what happens? i start and cast burning head, can he cast his burning head or does he have to dispell mine first? how does the rules here work with the same endless spells?
Both models can be on the battlefield without any issues. There is no restriction of only 1 Endless spell on the table at a time.
They can. Otherwise game balance would be severely affected. Some lists basically require a certain endless spell, so opponent armies would take it and cast it just to deny them. Which would suck.
interestering..... so each player can have his own endless spells, bound endless spells dont care at this rules.
They work exactly the same as all other endless spells. They even count as them. So you cannot have a Balewind Vortex and a Bound Balewind Vortex, but both you and your opponent can have one.
so in heavy magic matchups like seraphon vs cities of sigmar there could be a moment where 2x geminis, 2 quicksilver swords and 2 burnings heads are flying around?
That'd be quite awesome I do still hope we're going to see more neutral endless spells though. Stealing spells is underwhelming for most of the faction spells as it doesn't hurt the casting faction in most cases...