Need a translation of this sentence into idiomatically/grammatically correct Mandarin

[TheDoctor]

I need to say the following to a class of English students in grammatically/idiomatically correct mandarin

in a way that will be taken as self deprecating/ modest / empathetic / joking, and not as a serious statement, as it's meant to help my students feel at ease on their first day of class. This is starting from mid-sentence as I'll be saying this in the middle of an english explanation.

"because my mandarin/chinese is terrible/reallybad/awful and you won't learn well if I speak it"

any help with a translation will be much appreciated =)

BTW, this will be coming after the english statement:

"The final reason that we'll only be using English in this class is......."

[imron]

Speaking from experience, it's much more fun if you don't let on that you speak/understand any Chinese

As it's their first lesson, I suggest you also lay down the law regarding students speaking Chinese in class. I'm a little teapot works wonders, but if you don't do it from the beginning, it's difficult to try and change things midstream.

[TheDoctor]

"Speaking from experience, it's much more fun if you don't let on that you speak/understand any Chinese "

... With this class, I want them to know that I do speak a little because I want them to know that I empathize with their learning struggles.

If you were going to say the sentence I put above, what grammar/structure would you use?

[TheDoctor]

I think I have the first part figured out as wo3de zhong1wen2 fei1chang2 bu4 hao3, but the grammar and structure of the second part is really tripping me up.

Can anyone help me? Please? I really don't want to use a google translate result, as they are usually questionable in mandarin.