Dear you need to focus on the important things I mentioned earlier in order to get to max possible MMR.
Here are those again in order of priority.
GPM & XPM
Hero damage done, Hero healing done
Just a tip for knowing what types of game modes effect your MMR. Try to play ranked match, see what all game modes are available there. All those modes effect your hidden MMR once you play normal matches. Modes other than that, do not effect you MMR much.
You need to play almost 100 more matches to reach level 20 profile.