Its this sentence grammatically correct
No.
and what does it mean?
The expression "full circle" means "all the way around and back again." It's always used figuratively.
“I am full circle.”
If someone has a belief, rejects it, and then returns to it, the person might say, "I've gone full circle."
For example, someone might say: "I was raised a Catholic, but I left the church a long time ago. But after I got married, I started going to mass every week. I've gone full circle."
We can always help you more if you tell us where you got the sentence you're asking about.