Hello Siljo,
Thank you for using Apple Support Communities. Based on your post, you'd like to turn off the eSIM option and learn more about using it. We'll do our best to assist.
You wouldn't need to turn off eSIM, since it hasn't been set up yet. Check out: Using Dual SIM with an eSIM It explains how to switch between lines and how you can use it functionally.
This also answers your second question under section, 'Make and receive calls' it states; "To avoid missing an important call, you can turn on call forwarding and forward all calls from one number to the other. Check with your carrier for availability and to find out if additional fees apply."
Another helpful resource: If Dual SIM with an eSIM isn't working on your iPhone
Hoping this answers your questions, take care!