judge my english accent and guess where i’m from

You said "I have 18 years old" so I would have to guess a Romance language, but that's kinda cheating... I'll say France, your accent kind of sounds French

It's pretty hard to tell, but I'll guess Chinese I've heard a few Chinese people making the "I have ... years old" mistake before, and your way of speaking kind of reminds me of a Chinese friend of mine. It's just a guess and I could be totally wrong tho

This sounds like a Portuguese accent to me.

Spanish, "Yo tengo 18 años" as you said I have instead of I am

Argentina?

It has to be Brazil!

I'm surprised that nobody has said any Slavic country here. The grammar screams Slavic. Could be Russia, Ukraine, Belarus etc. I'm saying Belarus because your name is Zena, like the singer Zena from Belarus.

My bet is you're a native speaker of Portuguese, probably from Brazil

You don’t sound native, but you don’t have a “super strong” accent, it’s noticeable. I’d say you’re a portuguese speaker.

Spanish or Portuguese

I can understand that it is not a native, but the accent is not bad. It's okay. There's no need to try to cover it up. You have to remember that your accent is a part of your charm and identity.

I would guess Brazilian? You speak singing!

You sound cute? Are you Asian?

Brasileira?

Bro give the answer already!!

Greek/Cypriot based on the name

brazilian - the melody or rhythm of speaking gives it away