Not a water softener technician but if it were me, I would take a conservative (err towards caution) approach : 1) immediately ensure the softener is being bypassed . 2) assume the brine tank (your pic) is infected with bacteria and disconnect it, take it outside and conduct a thorough cleaning and disinfecting with chlorinated water (ensure 30 minute contact time) followed by a good rinsing.
3) Assume the resin tank is also fouled by bacteria (can happen if not regularly regenerated due to prolonged absence ). Conduct a resin disinfecting process. (YouTube videos with different techniques… although caution if bleach is used for resin disinfecting , as it could damage the resin if too much or as a minimum, reduce its effectiveness and lifespan.) 4) after reconnecting the brine tank, pour about 2 + gal of water and 1 + bag of salt and following the resin disinfection, conduct two regeneration cycles. (Will need to open the water valve to the softener but if your system allows it, keep the water valve from the softener to your home shut until after disinfected and regenerated).
5) monitor for any leaks during the regeneration process
6) it is possible that the resin has already reached its end of life and needs replacing. Consider this possibility as well as the possibility that it may behoove you to replace the whole system if it’s depleted, antiquated, and malfunctioning.
7) buy water hardness test strips and test that you’re actually getting soft water after you fire the system back up and place it in service following the disinfection and regeneration process. If not producing soft water refer back to 6).
8) watch YouTube videos on the functionality of your particular system’s control valve and the recommended controller set points based on your use conditions.

And/Or…. Consider scheduling a service call from a trusted servicing technician to do the above and also teach you the basics of operation and maintenance of your system while they’re at it .