Is it possible to socialize feral cat?

Hi! I have 2 feral cats I’ve started feeding recently. The person who fed them before has now moved away with little notice so I don’t know much about the cats. I only know the older male is maybe 4-5 years old & the smaller female is less than 2 years old. Since I live in Germany, I felt comfortable contacting a local shelter and they helped me get them fixed. They are currently at the shelter, been there for 2 weeks now. My question is… would it be possible to socialize these cats?

I had to use a humane trap to get them to the shelter. They were both very scared/hissing/growling when I got close. The male has had human contact before (previous feeder took him to the vet a year ago) but is very wary. The female one hasn’t had any physical contact with humans until now that she’s at the shelter. From what I’ve been told, they are still very scared but not as aggressive as when they first got there. They don’t want to be touched but the employees are able to put their hand in the kennel without having their hands bitten off.

If they can’t be socialized they’ll be returned to where they originally lived.

Sorry this is long but I’m curious on your opinions, do you think there is hope or would trying to socialize them cause more harm than good? If there is hope, what would be the best way to try to socialize them?