Sadly the native dictation utility doesnt work that well to start with. They do "learn" though over time.
The best software for this is Dragon Professional Individual. Sadly this is rather expensive
https://shop.nuance.com/store/nuanc...4441&cjevent=e323bb01698011ea83e5004e0a1c0e0e
Originally Nuance had a product called Dragon Dictate Professional for Mac but it was discontinued in 2018. The PC version is still highly recommended but you would need to instal Parallels in order to run Windows on your Mac to use that.
Have you tried turning on Enhanced Dictation in System Preferences > Dictation and Speech?