well you are bronze so you dont have the skills to become godly with ANY champ or role.
in league of legends, patience is the most important thing. patience and careful positioning. greed and the desire to be cool are the absolute downfall, so if you want to learn the game, ESPECIALLY marksman, you have to practice being super patient and CHILL and whenever you feel, in your brain, in your body, the desire to "do" something, sit back, take a deep breath and recall that you are playing this game to win, not to be cool. you need to chill 100% to win. that goes for EVERY CHAMPION IN EVERY ROLE, but some champions forgive hasty plays to an extent while marksmen never do. if you get hasty, if you fuck up, if you lose your cool, you will lose the game for your team and it will be your fault and only yours.
the BIGGEST PROBLEM in league is that its basics are very obvious. almost too obvious, so nobody actually realizes them, especially not marksmen. they think like "Omg i need godly mechanics i need this i need that omg no peel" but while you also need all that, it makes up only about 10% of what you need. the rest is gamesense and CHILL.
if you start playing less retarded and more relaxed and stop suiciding all the time (whenver you die and its not as the last person in a teamfight, it means you lost your cool and positioned like total shit) you will be diamond 5 in no-time.