I prefer
ebay for both selling & buying used stuff. Though ebay charge for the listing. It's more safe than olx & quikr kinda DD sites ... Since most individual sellers on ebay list at a higher price. If you list it for 1-2k lesser than them. Your listing will get attention from genuine buyers ... If the item is out of warranty. Give them a week return back option to attract. Add 10% to your intented price in your final listing price. You could cover ebay + paisapay charges, shipping charges etc ... You could give 5% extra discount if there is any negotiation for a reputed genuine buyer ...