Hello @SunriseChristoli, and welcome to the forum!
Since you whether name your version of Krita, nor from where you downloaded it and which operating system you use to run Krita, I can only hope you don’t use Android, because there my hint won’t help you.
There is a plugin for Krita which can help you with your issue, because it is made especially for reducing the count of nodes on a shape, although the initial problem to solve for that plugin was a different one, it will do what you are asking for:
The topic here in the forum is:
And the GitHub-Page where you can download the plugin is:
If you don’t know how to install a plugin in Krita, here is a small guide:
The easiest way to install plugins in Krita is to go to “Tools” >> “Scripts” >> “Import Python Plugin from File…”, then in the dialog that opens, specify the path to the plugin, so browse to the downloaded ZIP on your PC or Mac and select the ZIP file you just downloaded and click on the OK-Button to confirm the selection, confirm the next dialog box(es) and possibly asked questions (depends on the plugin) as well, then restart Krita and then, depending on the plugin, set up the plugin to your liking or use it right away.
Michelist