@NinaPop: This is possible to achieve, although you will be required to customise each app notification settings manually. With this in mind, please head to Settings > Apps > Calendar > Notifications > Notification categories > General notifications > Show notifications > Lock screen > Show content. To hide specific app notifications e.g. Messages, head to Settings > Apps > Messages > Notifications > Notification categories > New messages > Lock screen > Don't show notifications (or Hide content).
Now, head to Settings > Notifications > Detailed. Also, head to the Calendar app > Tap the 3 lines in the top left > Reminders > Tap the 3 lines in the top left > Tap the cog in the top right of the pop-up window > Alert style > Select your preferred option here.
Another approach you can take is to head to Settings > Notifications > Do not disturb, and toggle this option on. Now, in the Exceptions category below, select Alarms and sounds > Alarms (on) > Reminders (on). Go back, select Apps, and allow Calendar and Reminders as an exception. Let me know if this helps.