If you are struggling to complete any stage here are some strategies to help you

Speed:just go fastly through the course while spinning to avoid the damage.if necessary you can shoot smart bombs.

Power: take your time and try and destroy every enemy in the level.

Ability: either go fast and avoid damage and shoot straight ahead.
Or you can go at medium pace and shoot whatever ever is visible without moving to far from the middle of the screen.

On the first level if your finding the boss hard then do it again and destroy all the machines in the water and you'll follow the F guy to a much easier boss.