How do I restore deleted text messages?

Unless you house your messages in iCloud, they are saved on your latest iPhone backup. Restore that backup to retrieve the messages that were present when the backup was created.

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

recently my text messages with two of my everyday contacts suddenly are gone, ive had those conversations for years ,not including all the shared pics and videos that were randomly shared in the texts ..why would they just disappear? My settings have always said keep messages forever

Unless you have a local backup on your computer, it's gone, deleted.

Messages are not part of an iCloud backup.

That is not correct, they are included if one has not turned on iCloud Messages.

We will see, if OP has iMessages On or Off in iCloud

Yes we will but they are part of an iCloud backup if they have not opted into iCloud Messages. You stated Messages are not part of an iCloud backup, period.

Yes, I did assumed.

Also^^, I’ve never backed up anything or ever figured out this cloud thing