As you are not comfortable with coding, you can try using Recent Posts Widget Extended plugin. It allows you to specify the number of posts per category that you want to be displayed.
Follow these steps:
- Install and activate the plugin.
- Head to Appearance > Widgets. Add Recent Posts Extended widget
to your sidebar. - The widget menu will expand to show its settings. Here, you can
choose your desired category and specify the number of posts to
show. - Finally, click on the Save button to store your widget settings.