Hey i have heard from a friend there is a sword of fire but he cant remember where he got it from. Can someone tell me where i can find it..

In Tales of the Sword Coast, there is a longsword Flametongue, don't remember stats.

Yeh but where in totsc is it in durlog's tower or ulgoth's beard or is it just some new weapon added somewhere in the game?

The Flametongue is located at the bottom level of durlags tower, in durlags lair. By entering a secret door to the east side of the "Green Chamber" (you'll know it when you see it), you will find a few corridors, traps and rooms. Its in there somewhere. Happy Hunting