So, not an expert here, but i have a few insights.
First, you really like your health items. Specifically when playing voli, although you could see it a bit in your other games. Watch how is getting fed and optimize against them, as with a high natural health tank like voli, you can afford early resistances.
Second, you die too much. Even in the games you win, you have a lot of deaths. I can't watch your games, so I can't give you the specific reason, but it is probably a mix of these 4. 1: Map awareness. 2: misjudging your power/tankiness. 3: Not grouping properly 4: bad positioning in a teamfight. Map awareness is a general skill that comes with warding and practice. 2 is just knowing how strong you are with your current items, and how you match up to the other fed people. 3 is learning the flow of the game, and can be better aquired through watching other people play (ranked soloQ in the bottom right of the client is wonderful for this) 4 is the same as 2 and 3. know your champ, know your role, know where you have to be.