Language is a living protocol that you can only learn by listening people use it and using it yourself constantly. Whether a made up word makes sense syntactically and grammatically doesn't matter. In fact whether it's in a dictionary also doesn't matter. What matters is being understood. So you need to use words people know. Sometimes you're in a position to make up a new word, when you need to. Talking to students about when their exam is... is not one of those situations.
And a heavy accent literally corrupts your communication. On top of making it hard to understand what words you say, your intonation becomes completely unintelligible, because you're speaking English, but intonating in another language. You're literally not speaking entirely in English. Strong Indian accent is especially infuriating for this, I find it very hard to listen to and understand.
And by the way, made-up words and strong accents are ESPECIALLY annoying to OTHER non-native English speakers, because we have an extra hard time parsing this on top of understanding a non-native language already.
I should know, I'm a Bulgarian, so... (I have slight accent).