Pronunciation or tone, intonation ?

Hello everyone, I am reaching help because I have an issue in speaking skill that I don't know how to fix it . First of all, there were many time when I talk with native people and they didn't understand some word that I said. For example:

Me: sorry sir/mam, may you show me where is the "restroom"? / hey, do you want a "pizza"? or what does the term" issuing authority" mean?

People that I talk: you want to know "where"? / Do I want "what"?/ what is that word again?

Me: oh, restroom sir! / pizza, you want some? / issuing authority sir,ma'am/

after 3 or 4 time repeats, sometimes I had to write it down on the paper, and they finally realize Ohhhhhh restroom, or ohhhh, pizza, or issuing authority...

The thing is when I asked that what was wrong in my pronunciation,I just repeated exactly what they just said. They just smile and said I don't know.

I am really confused because this is 50/50, not all the time but not rarely either. I really want to confirm the problem so I recorded my voice, it sounded normal to me, I asked some of my native friends and my nieces ( who was born and raised in the US) write down some words that I told them, they wrote all of them right.