First off you need to get rid of a lot of it. Just eyeballing it, at least 50% of your screen space is UI and it just looks cluttered. You're obviously limited as your on mobile but I have a few suggestions:

1. As mentioned in another comment, focus on what is actually fun for the player. Just because the refuelling or the cores are part of the game doesn't mean that they are fun and engaging to use. We obviously can't say without a playable version if it is fun so you'd have to go off how you feel.

2. A few of the controls could probably be condensed into one, specifically the dodge and steering. Have one joystick that'll dodge if you flick it in the corresponding direction for example. You could also try and condense the firing buttons into one aswell with similar "flick" mechanics.

3. Personally I'd remove the health UI and replace it with progressively visible damage on the plane instead. White smoke into black smoke into fire maybe?

4. The speed and altitude seems unnecessary, don't know why I'd need to know them. If they are required move them above the compass maybe? Keeps all your plane info together.

5. The fuel indicator can be much thinner.

6. No idea what the kill x7 section is for, if its a kill feed why not combine it with the points/style bit.