Rigolo Privé ?? (private joke)

Two of my French friends were joking around the other day and I went out on a limb, constructed a sentence and asked whether it was a private joke, «une rigolo privé » ..
I thought, surely, they must have private jokes- and they would understand me if I said that.. But they just started laughing hysterically..
I guess they understood but thought it sounded like something a Canadian person speaking French would say :) Turns out- they say “private joke” in English.
In the beginning, you are bound to make many mistakes in communication but if they are funny, you’ll be more likely to remember the words or the grammar.
The same thing happened to me at lunch the other day- I asked “Vous avez mangé bien?” which sounds like- “Did you eat properly” (like with good manners :) when really, I meant to ask “Did you eat well?”, (like did you have a good lunch), which is said “Vous avez bien mangé?”.. Simply changing the place of the adverb changes the meaning of the sentence…
Don’t worry- French people normally help you with your pronunciation and grammar :)