infiniteloop wroteBack in elmazad times it was much easier to sell, perhaps it had more serious buyers, OLX made so much ads about their own website that too many cheap people think they have the rights to bother sellers by asking 1/2 even 1/3 of the published price.
If they see you agreed to lower a bit the price they will ask for a lower price again and again and in the end they don't even buy.
As for African spammers, they should do like ''Leboncoin'' which is similar to OLX in France, they simply hide emails and phone numbers of the sellers to any ip outside France, OLX should do the same, or at least block African ips.
One thing that helped me a lot in greatly reducing the number of cheap people and spammers contacting me is disabling the option to be contacted through chat. I also mention in every post that I don't reply to sms. If someone isn't willing to make the effort to save my number and call me or at least politely contact me on whatsapp, then they're not worthy of my time either.