hello i got a verry seriours problem. \when i flashed rom i cant see launcher and gapps .. please can you help me how to fix this problem

Hello guys, I got a very serious problem. My father have bv6000 and after 1-2 days used phone , Having used the phone more than 1-2 days began to show ads on advertising, whether in administration or just the menu. please tell me how we can fix this problem