What is my dominant function?

You seem gamma to me, and possibly Pi-lead, but I wouldn't rule out the possibility of TeNi. We've had TeNi examples, especially males, whose expression is calm like yours, and who speak more slowly and "carefully".

But it's better to wait for more input!

I am still new to this. But watching your video for the first time. I see Ni more than Se. Your eyes look hypnotic to me and even though you are staring straight ahead, it looks like you are actually looking through me, not at me. So I would say NiTe or TeNi. But just my impressions...NiTe.

(Also, just for the record...I thought NiTe before you said that your best friend thought you were NiTe. Also, be sure to read my new signature that I just made...my own personal disclaimer.)