Can I use the GPLv2 library in my application for free?

Question

Android

Hello, gentlemen, please tell me if I take a library that is under the GPLv2 license. I don’t understand a little what to do with it, in the sense with this condition the library is licensed under the GPLv2 license. Do I have to pay someone or do I have to write my own application and put the source code in my account for public access? And if I post it in my account for public access, and then I make updates to the application, should I publish them too? Please clarify me in this, but I'm already confused in terms. The application will be free, there will be ads, the application itself will simply use one library with this license and I would like to immediately understand if I can use it.