Script for calculator buttons

Hello everyone, I decided to make a calculator but I ran into the fact that I couldn’t write the code for the buttons, can you help? and in general it would be good if you also explained what is happening in the code, since I am still a beginner and am learning to understand the code, otherwise there are very few lessons on GDscript on YouTube and they are too short and uninformative, thank you for listening

I can also send my project to you via telegram @Fidence_Official

I’d suggest this video on YouTube. ’ Let’s Build a Calculator in Godot 4 - Part 2 (Logic Coding)'. It is 20 minutes, well paced, informative , shows and explains the code and will allow you to implement the code on your own, which is key for addressing your goal of your question is ‘learning to understand the code’.