On the third that he persuaded me to invest more money so that I will earn bigger
This is where thieves catch newbies easily because they know that at the mention of bigger gain they will rush in. Anyone can promise you anything online but first mark sure they have a track record you can trust. Since he chatted with you on WhatsApp that means you have his number. Trace the number and know how you can track him.
I think we must be careful about the social media accounts we have so that we can use them well and with security we can use
The story in the OP has nothing to do with security of social media account. It was greed that caused op getting himself scammed