I'm new in Python programming If there are websites where developers can share their add-ins and scripts that will be great. do you know any? unfortunately, arcgis.com only provide very few
ArcGIS Code Sharing seems to be the site that you are looking for.
It claims to enable you to:
Search, browse, and use code, scripts, models, add-ins, widgets, and more.
There were 48 results when I searched there for Python AddIns just now.