Thanks for the suggestion!! Which language I should know?

Learn C,C++ and master in Java and C++. Get the basics and concepts. Mostly MNCs asks basics. You can install the INDIA bix app to know how the companies ask questions. If you want to join Google and Microsoft then go for hackerrank,leetcode,codechef,hakerearth.
They have many questions to know how problem is solved using logic building. And geeksforgeeks has every question company wise. There are many things. Just do this much. You will get a job. And also aptitude and reasoning. Verbal and non verbal also. Prepare this much to a expertise level in 3 years. You will get a job very easily

For gate also these will help you. Use gradeup to practice. And browse in Google for previous year papers. You will get it.

OK thanks