How can i uninstall messenger (standard application)?

Removal isn’t possible. If you don’t wish to use it, simply sign-out:

Settings > Messages > Send & Receive > [Your AppleID] > Sign Out

As for modifications to the OS, or jailbreaking to obtain root-access, these are not topics permitted by the Terms Of Use that govern participation within the Apple Support Communities (a link to which you’ll find here - https://discussions.apple.com/terms).

The native Messages App is an integral element of iOS/iPadOS; it cannot be removed.

Messenger is third-party App.

See >>> Delete apps from iPad - Apple Support

You just can't remove it, it would take up such little space it would make no difference

Well you can't.

You posted the question and got the answer, you can;t remove it.

Or buy an iPad with plenty of space and you won't have to worry about one tiny app.