To start with treat this as 2 separate projects.
One project will detect data from the solar panel and display the results as simply as possible on the PC serial monitor.
The other project will allow you to figure out how to display simple data on an LCD screen.
When you can do these things separately it will be time to combine them.
Bear in mind that if you want help here it will be easier to understand your solar panel code if it is not confused by LCD code. And it will be easier to give advice about the LCD code if it is not confused with solar panel code.
...R