Some people might disagree with this, but try to get good with 1 hero and 1 hero only (I have hundreds of hours on Zarya). The most important thing to do is get the fundamentals down (muscle memory, reaction time, leaning animations to predict etc). And then try to expand into getting good with 1 hero per class. Another thing is don't be stubborn because filling what your team need is one of the best way to carry. Team comp is a win condition. And lastly learn and play what is strong in the meta and learn the counter picks. At least that's what I tend to do when I start any game tbh. I'm only a Lowly diamond so take my tips with a grain of salt.