Unable to crack interviews

I have 4 YEO, currently in a support role and trying to switch to an android developer role as 3 YEO .. gave many interviews, more than 10 I guess... Today again I had one and I had a lot of expectations from it as it went very well.. only 3 4 questions I didn't know.. But I still got rejected.. I am not able to understand what I am doing wrong.. because everytime I there is some question I am not able to answer properly.. also sometimes I know the ans but I can't frame it or define it.. but I try to explain them by example..

It's very frustrating to get rejected again and again 😓