Hallo @antonio_rueda_toicen
In our last LL we came across the word “einer” in this phrase: Es gibt viele Flüchtlinge aus … Ich bin “einer” von ihnen. (I’m one of them.)
In this case “einer” is used as a pronoun. A synonym for “einer” would be: jemand
I hope this helps to answer our doubts. 
Bettina