It’s hard to give general tips for Winston beyond just playing more as him. You should have a general idea of his counters and weaknesses and what you should be doing as Winston, but putting them into practice is a little different than just knowing what you need to do.
Prioritize breaking bad habits you have as Winston. My guess is you probably jump in and immediately bubble. Don’t do this. Don’t always use jump pack to engage, especially if you find yourself getting burned down quickly. Be a front line presence until the enemy team separates themselves a little bit, and then jump pack onto supports.
Most of Winston, at least in my opinion, is less on mechanical knowledge and more about understanding the ebb and flow of a game, and understanding that said ebb and flow is going to change with every game. You just need to learn how to read situations as Winston. I feel like if reviewing VODs of your gameplay as Winston is invaluable because it’s a lot easier to see what you should and should not do in any given situation, a lot more so than simply telling you “do this, not this.”