Getting Low KDA

So today I played Talon mid, and I find myself doing poorly. We didn't lose, but I find this unacceptable to me. A 5/6/15 KDA of Talon as a mid... Like I don't know why how am I getting a somewhat support kda but mostly I died to a player playing Master Yi (killed me 5 times while TF killed me once.) So I asked myself, "am I playing too passively?" Yes, I believe that I am still a noob in LoL, still trying to improve and be a pro and all that, but I need some help on how to get more kills and be more efficient to the team.

There are 3 things I find that are mistakes to me:

1. Playing too passively, not playing aggressively enough to get kills
2. Bad decision-making (kind of ties to number 1, like should I go in or stay back to not get killed by mid or jungle)
3. Not building the right item builds.

Is there any solutions to this (3 I could solve quickly, but 1 and 2 is what I am struggling at.)

To conclude, I am asking, how to play more aggressively to get more kills but at the same time not dying to them (playing both aggro and passive), how to make good decisions, and how to overcome the fear of dying from your laning enemy and enemy jungle.

Any tips will help!

P.S: I played a lot of support, is that the reason why I am playing too passively? Also does it help if I learn from pros on stream, analyzing what they are doing so I could improve?