>>>This bike is for sale for 300$. <<<
A bargain

>>>Is it steel or aluminum ?<<<
steel
>>>sticker that say something like this: "Colombus acciaio livacron max ellssi orientate"<<<

The sticker describes the tubing used as Columbus Max- a differentially butted, nivacrom steel with a multi-shaped & oversize diameter crossection- state of the art and top of the line in performance and technology for the time. It is a tubeset that has rightly earned a cult status for quality amoungst the cogniscenti.

>>>Also, would it be good for single speed (It is not required)? <<<
Converting this fine roadbike to a single speed would be a travesty, imo.