how can I get back my photos and videos after deleted for 14 days on iPhone?

If you deleted the photos and videos 14 days ago from the regular Photos Library, they are still likely in the Recently Deleted Album........Photos > Albums > Utilities > Recently Deleted.

But, if you are saying that you deleted the photos and videos from the Recently Deleted album, they are permanently deleted and gone......unless you made separate backups on another device.

Recently Deleted is found under Utilities. If you deleted the photos and videos from Recently Deleted, you permanently deleted them. They are gone......unless you backed them up to another device or another service before you deleted them from the iPhone.

I suggest you actually READ the answer posted in response to your original post.