You do not have to know all English Grammar
Many new TEFL teachers are daunted by the prospect of having to teach grammar to a class as they feel that their knowledge in this area is extremely limited.
Many students who have studied some English are often aware of the various tenses and related terminology.
If a student asks you about a grammar point that you are unsure of, tell them that you will get further clarification and shed some light on the language item during your next meeting.
https://www.itefli.com/teflblog/problemsteaching-grammar/