Many Android devices come with lots of built-in apps that can take up storage, update themselves and send spam notifications without you even using them!
To uninstall/disable the apps you don't need, go to Settings then click Apps and choose an app that you don't need, then click Uninstall/Disable and accept the warning
Aslong as you don't disable Dialler, Messages etc or "Google Play Services" you will be completely fine
If you uninstalled, that was it!, if you disabled, you'll need to click the three dots in the top right corner then click "Uninstall updates" to free the storage space
(And if the app re-appeared, disable it again)
Then restart your phone, you will notice a massive amount of storage freed, and significant improvements to speed and battery life