how to reset my macbook

See the instructions in this Apple article: What to do before you sell, give away, or trade in your Mac - Apple Support

Note that the instructions in item 2 in that article only apply to newer Macs; older Macs will use steps 3 through 9 instead of step 2.

This may help if you decide to go this route:

Erase your Mac and reset it to factory settings - Apple Support (CA)

Everything will be erased. I recommend a backup just in case before doing this.

This page can help too, if using Intel based Mac:

How to reinstall macOS - Apple Support (CA)

If you want your data erased, then you will need to wipe/erase the disk first before installing Mac OS.

Hope this helps.

Adam