I don’t know what to do, I dropped from Emerald 2 to Platinum 3, I don’t know what I’m doing wrong.

I’m a Skarner OTP, but I haven’t been able to win many games and I don’t know why. In the last game, for example, I went 5/0/15, secured all the dragons, Baron, Herald, and Voidgrubs, and still ended up losing because my top and bot kept getting picked off and dying all the time. what I do to climb to emerald again