Can somebody guide me whether should I learn checkpoint firewall? Is this firewall still in demand ?

It is completely up to you. My organization is not only using checkpoint firewall in their 4 global data centers but they have recently started a project of upgrading them to the latest version. 

Palo Alto is the firewall of choice these days. I switched jobs in couple of companies and they both have Palo Alto firewall in their data centers. Though they also have Cisco Firepower at the internet edge.