By the way, you definitely wouldn't use أنا in that sentence.
Ah, I see what you meant.Really? I don't see why it would be grammatically incorrect. I realized I should have put "أمزج", but if وأنا was there, it would be read as "while mixing (in)..."
To add to Elroy's comment, I thought I'd let you know what's incorrect in أحتوي and the أنا :This might be too loaded, but I'll give it a try:
عندما أتكلم الفصحى أحتوي عليها العامية المصرية
أتكلم الفصحى و(أنا) مزج معها العامية المصرية
These were fun, Josh But I hope you won't really use them, or else you'd need ennak tewazza3 ma3ahom catalogue besh-shar7
That's clever Josh although for this one I'd suggest (faSdaja), just for some gut reason I prefer to retain the jeem.