Firebase api is good simple and alright but when you want to add it to your android project , you want TO KILL YOURSELF. OK first gradle works then say oh you should update your gradle you update it . then it says cannot resolve firebase:core WHaaaaT? OK YOU SEARCH FIREBASE API FOR AN ANSWER THERE IS NOTHING THERE. then stack overflow come to your help you should update some FUCKING package that firebase didnot mention you should update and all this time you say dns is wrong , firebase is filtered your country again, and after you update thise tow package you found out that you should update your android studio too for just one line code(firebase mentioned this but I said noooo it's just optional) .