OLX is basically a second hand flea market. Only form of protection you have is the price: should be so low as to not hurt you much in case the product is defective and seller ghosts you. I never had a problem and bought many things on it, most expensive a ZX Spectrum clone with CP/M and floppy drive for 400 euro. My brother bought a couple of brand new smartphones for like 50% discount and they were genuine. It works more often than not but there's always the risk.