Audacity software

Hi… I hope you’re fine… I have a question…i have this video…
I'll be back (Police station assault) | The Terminator [Open Matte, Remastered] - YouTube… start at 18 second…terminator chracter is talking…i cut the scene…i removed its vocals…and I recorded my vocals according to scene…but when I put my vocals in video…it sounds fake…it sounds i just voiced over the scene…that’s it…it doesn’t sound like i am standing there and talking…is there any one who can help me in that… how can i mix and master my voice to sound like I’m standing there and talking…for audio editing I’m using audacity…software…:blush: