Open Gmail
Click the gear icon
Select See all settings
Open the Filters and Blocked Addresses tab
Click Create a new filter
Enter the sender’s email address in the From field
Click Create filter
Check Never send it to Spam
Check Always mark it as important if needed
Click Create filter
Open an email from the sender
Click the three-dot menu
Select Filter messages like these
Create a filter and apply the same settings
Add the sender to your contacts
Move any message from the sender out of Spam if it was filtered there