GUI improvement and bug finding

I am working on improving the UI of my application and would appreciate any suggestions or help. Here are the main areas I am focusing on:

GUI improvements:
- Maybe put a nice background
- Change general graphics buttons and text

I would like suggestions on how to **improve the user experience** with more intuitive navigation. Design suggestions to make the **interface more modern** and intuitive. **Bug tests** to find out if there are any hidden bugs. Any feedback or pull requests would be appreciated.