How do I improve the UI of a webpage that expands as you use it? [on hold]

I have a website that constantly gets bigger and bigger as a user uses it. It is not yet complete, although I believe it is time for a better UI. So, how do I make it so the user feels more welcome. Currently it's a blue and orange, with round buttons and text boxes, but I was thinking of making changing it to make the textboxes and buttons rectangular with thick, neon-light-blue borders and a black background, somewhat similar to the Zorin OS linux distrobution. Is it smart to use a darker theme with a dynamic page, or should I keep it the same?