How do I reset my Mac mini?

How do I wipe and start fresh with my Mac mini? I cannot find a restore point or how to reset my computer like I used to on my old pc. Helpless and overwhelmed in California.

My computer skills seem to have gone down hill. My mac mini feels like it is duplicated and I feel like a Linux system has become an invisible gate keeper and I need to verify why my computer indicates I am not connected to the internet.

• I have this big search bar that wont go away.
• I also need help to make sure all my documents are saved in my iCloud.
• Is there a service I can purchase or a step by step do it yourself app? Or an outline of what is needed?

This dummy needs help desperately. Any suggestions?

[Re-Titled by Moderator]