Hi,
If the headphone socket is internally damaged it cannot be repaired, it needs to be replaced.
Here’s a [https://www.youtube.com/watch?v=hvCTCLizhMQ|video] that shows the teardown of the phone that may help to get access to the headphone jack.
I cannot find a replacement spare part online but thought that [https://www.ebay.com/itm/ZTE-Majesty-Pro-8GB-Black-Straight-Talk-Z799VL-Cracked-Screen-Parts/173810233872?hash=item2877e5b210:g:bgMAAOSw-kdccsiz|this] may be an option to consider as a donor parts phone, given that the price is OK where you are.