Help with Google Android Project

Hi,

I have to add a jar and two dependencies to an My Android project and I need to split the project too.
I tried several times and I'm getting different results every time.
Sometimes I don't have the option to build the signed apk. I don't have the build.gradle file in the project and I need it (because I don't know others ways to add the two dependencies). And the result apk (that I don't know how to split) is much bigger that the original apk build it with Unity.
Can you help me a bit with this? Some advices?