What am i supposed to do as a midlaner my botlane is 1/12 by the 15 minute mark

Edit: title should be "a midlaner when my botlane.." oh well, cant fix titles for some reason

I literally have no clue what im supposed to do to win

I was playing and was doing DECENT. I was 2/1 at the time and was trying my best to pick off people, except the enemy was giving them 300 hp/sec (and if she wasnt near them she could just globally heal them for like 500.)

So yeah what am i supposed to do in this situation because i literally feel like i do not affect the game.