If I could teach English for Caritas' night courses?

If your qualification can meet the requirement of Caritas, you should take action to apply, In another side, you should consider
1) whether or not you have a cerficiate of english teacher.
2) whether or not you have an experience of teaching. If you did not have this kind of experience, I think that the success rate is very low.
anyway, you must try as you did not need to pay any money. Don't just sit and think. You should take action and get the result - good or bad.