Duoing with friends

Hey there everyone so my friend Justin got into league of legends a few months ago and left it and came back and i wanted to teach him how to play at first he played fiddlesticks which made me so mad because he sucked at him and now hes playing Evelynn which is better but he builds devourer which isn't the best for her so its not easy teaching him to play but now hes decent and doesn't feed every game but hes still not the best player and we have a crap ton of trolls in our games but whatever we can still win most games and he for some reason never gets a single drag unless we scream at him which i find funny.Lastly I feel like he will be good once hes lvl twenty eight i feel like then we will be able to duo for fun and not just because i want to help him.