When i. Listen to my veidos my sound goes off and on. How do I fix it

Just check with the sound profile by getting into setting option and check if the volume is in higher mode and also change the tone if it is in silent mode.If everything is working fine then reboot your phone by this steps1.Power off the phone.
2.Press and hold Vol+ key and Power key simultaneously for about 10 seconds until the some option appear on the screen which are reboot system now; apply update from sdcard; wipe data/factory reset; wipe cache partition.
3.Use Vol+ key and Vol- key to move the cursor to "wipe cache partition" and press camera key to confirm it.
4.After 5 seconds, the cursor will be on "reboot system now" again and press camera key to confirm it. The phone will reboot automatically.
Backup data to SD card before you troubleshoot.

Have you dropped your phone or got it wet somehow? If you did, you could have got your phone damaged. You need to send your phone to ZTE for repairs.

You can also just restart your phone. That usually solves any issue that suddenly comes to my phone. But if it doesn't work still, you really might need to have your phone repaired. Good luck!