Hi silas286,
To change the options for Screen Time, open Settings > Screen Time > App Limits. Depending on how your friend set this up, your friend who holds the password should be able to remove the Messages app from the app limit option. They may need to set up the limits again to remove Messages.
Additional guidance is here:
"Set limits for app use
You can set a time limit for a category of apps (for example, Games or Social Networking) and for individual apps.
- Go to Settings
> Screen Time, then turn on Screen Time if you haven’t already. - Tap App Limits, then tap Add Limit.
- Select one or more app categories.
- To set limits for individual apps, tap the category name to see all the apps in that category, then select the apps you want to limit. If you select multiple categories or apps, the time limit you set applies to all of them.
- Tap Next, then set the amount of time allowed.
- To set an amount of time for each day, tap Customize Days, then set limits for specific days.
- When you finish setting limits, tap Add.
To temporarily turn off all app limits, tap App Limits on the App Limits screen. To temporarily turn off a time limit for a specific category, tap the category, then turn off App Limit.
To remove a time limit for a category, tap the category, then tap Delete Limit."
This information is from the iPhone user guide, Set up Screen Time for yourself on iPhone.
Take care.