who the real heimdall is

Heimdall (Old Norse Heimdallr, the prefix Heim- means home, the affix -dallr is of uncertain origin) is one of the Æsir (gods) in Norse mythology. Heimdall is the guardian of the gods and of the link between Midgard and Asgard, the Bifrost Bridge. Legends foretell that he will sound the Gjallarhorn, alerting the Æsir to the onset of Ragnarök where the world ends and is reborn.
Heimdall is described as being so alert that he requires no sleep at all. He can hear the grass grow and see to the end of the world; he can hear a leaf fall. Heimdall is described as a son of Odin, perhaps a foster son. Heimdall was destined to be the last of the gods to perish at Ragnarök when he and Loki would slay one another.Húsdrápa and Heimdallargaldr
The lost Heimdallargaldr may have contained the following adventure which was also referenced in Úlfr Uggason's skaldic poem Húsdrápa of which only fragments are preserved:
Once, Freyja woke up and found that someone had stolen Brisingamen. Heimdall helped her search for it and eventually found the thief, who turned out to be Loki and they fought in the form of seals at Vágasker 'Wave-skerry' and Singasteinn, wherever they may be. Heimdall won and returned Brisingamen to Freyja