how would you improve the buttons on the top of the screen? To grab attention of the user I tried to change a bit their color (they are dark blue instead of black), but I think that they are not coherent with the rest of the screen.
Generally, circles are used to show information (think social media profile pics); we see them less as buttons.
Try making the buttons rounded rectangles. I don't think coloring the icons necessarily helps make them more discoverable, and color might compete with what the user is trying to do visually on the canvas. Monochrome might be the way to go.
It all depends on the product strategy
if the target is to be an advanced graphic processing program it's worth thinking about the menu comprehensively and holistic.
Or put the interface elements on the left side of the canvas with the addition of a text / description of what they are doing
Put your buttons at the bottom. When user looks for navigation buttons he well clearly see them.