Suppose you are giving a talk and in your audience there is a person who does not speak your mother tongue. Let's call them John.
Neither your mother tongue nor John's mother tongue is English. However, you can say some words in English and John can understand them.
As you are not comfortable speaking English, you are giving your talk in your mother tongue.
What should you say to John in order to apologize for not speaking English? I'd like examples of some possible sentences because I'm not sure I can construct a grammatically correct one. I'd also like the sentence to explain the reason given in last paragraph.