How to repair the headphone connection

@victorrcastro you are not telling us what you have checked or even what happened to it. It will also be important to know if you still have sound through the speakers. for now try to  to go from Control Panel go to the Sound Realtek driver. Disable it and then Re-enable it.  If that does not work you want to uninstall the drivers and reinstall the latest drivers for your audio.

If none of the above resolves this then there is the possibility that this is a bad headphone jack. Use the Dell Vostro 15 7500 Service Manual to work on your laptop. Your headphone jack is part of the audio I/O board (something like this)and thus replacing the board will also repair the jack. Just make sure that you check all the software options first.

While you work on your laptop, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has a device with the same issues as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.

Repair is War on Entropy!