You can simply download the TOI or ET app where you can get all the national and international updates and all the news articles. The GD process usually encompasses topics on current affairs which requires you to have a good knowledge of all the goings on. 

For the PI round no app can help you but you can check out some videos on YouTube about one's introduction and the general questions asked in interviews. Apart from that go through your CV properly and prepare an explanation for everything. For example if you have an year gap then you should be able to justify the gap. 

And sometimes few Institutes ask questions on current affairs in interviews so you can also download Testbook's current affairs app where you can get all the latest information. 

All the very best