Ok here are some of my pointers:
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You are using very basic shapes and quite basic colours. The wavy title box isn’t necessarily simple you could say but it doesn’t work with the other basic shapes having one complex shape.
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The yellow, blue and green don’t mix well together. Have a look at colour pallets they can be very helpful
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Maybe you could add a title to the UI in the yellow shape.
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Also you could move the yellow box up a bit more maybe so that the bottom of the yellow shape and the bottom of the red circle are at an equal level. Also it would give more padding to the 3 boxes in the middle
I do like the 3 boxes in the middle though, good choice of gradient for them.
Overall I would rate this a 5/10 but it is a good start. I am guessing you used something like powerpoint.