Hi 
Looks very clean and I like the black and white look, its modern enough in my opinion. Good job, especially for a non-designer

From a designer's point of view, a few small things could be improved. In my eyes especially:
The shape of the buttons is not consistent. It's not that bad, but I would round all buttons (like the green ones). Then the input fields and the buttons would not be so similar. That would improve the usability.
Also, in dark mode you can't see the input fields that well. I would make them a little brighter so they stand out more. Alternatively you could use a thin border for the input fields (also in the light color scheme).
The purple of the icons is too dark for the background color. Didn't check the contrast ratio, but it looks too low. I also think the secondary font color is too dark in dark color mode. You can test it for example here (and use the sliders to find a suitable color for better accessibility): https://webaim.org/resources/contrastchecker/
Hope this was helpful in some way :)