Level is deceptive, I’m barely in gold.
As for tips, whenever you die, think of what you could have done to avoid it. Were you by yourself? Out in the open? Made a mistake with an ability?
For D.va, if the enemy team has a Sombra, try shooting at doorways to find her. 1 point of damage will stop her invisibility.
For Brigitte, use repair pack on a teammate who is fighting a flanker, or on you of your teammates about to dive the enemy team.
For Mei, make sure you wave at everyone you freeze, then use your alternate fire for a headshot. You need to cancel the end of the wave to have time to hit the short but it’s worth it. Freeze, wave, headshot.
On a more serious note, try using her wall in more creative ways. You can block people off, but you can also place it beneath any player to boost them up high.