Can i example a running animation and add a gun and repose it the arm like running with that weapon without use 3part softwares to do that or i have to use animation software
Yes, as long you have such an animation, and there are actually free animation in this regard found under the market free panel. Free Digital Assets and Content - UE Marketplace The way you do this in Unreal Engine likely explained in these tutorials https://www.youtube.com/results?search_query=unreal+engine+tutorial+character+weapon