It sounds difficult, especially for many native English speakers who studied foreign languages with translation. But many schools have an “English only” policy for the classrooms, and there are many good things about this.
It helps students learn to cope in an English-speaking environment, which is what they will have to do if they need to use English outside the classroom. Presumably, they will be using English precisely because the person they need to communicate with doesn’t speak their language. It is easy enough to turn to your neighbor in class and ask for a translation, but this won’t work in the real world.
Learners need to be able to explain a word they don’t know (or go from an explanation to a word) and ask for clarification in English if they need it, and your class is the four hours a week to do that.
Also, part of the reason native speaker teachers are in demand is because their lack of local language skills forces students to communicate in English. You were hired likely in part to create a situation where students do not use their own language as much as they would in a traditional class. And similarly, if your students start discussing grammar in their language, you won’t be able to understand, so you will have to check that they’ve got it right anyway.
All that said, the reality is that translation still happens sometimes. What to do? Some teachers collect money from students who speak in their own language (and buy something for the group at the end of the term), some use some kind of red card/yellow card football system, but I tell my students that I’m a teacher and not a police officer or referee. I ask them to try to use only English and explain why that’s useful (pretty much as I wrote above here) but they are adults. If I hear a non-English conversation going on, I will often go over and pantomime that I’m listening so they know I’m aware of it and this often works. But there are times when students get so frustrated or confused that I turn the other way when someone translates.
I usually find the best way is to do what you can to encourage people to use English – the rest is up to them.