giving head

I'm new to giving head to my man. I keep asking him I can practice all the time and he seems to enjoy that and allow me to. He keeps telling me that I'm becoming a pro at it but I'm sure he's lying because he also said the other day that I always miss his sensitive spot like all the time. And he sounded fraustrated about it. 
Any tips? Usually we're in his car so with the position and tight space I am not able to get to his sensitive spot (the bottom side of his penis). 
We were grocery shopping today and I gave his daughter a lollipop which she finished in like 4mins and I was surprised. His comment was "maybe my daughter can teach you a few tricks" 😒 I'm so annoyed and so badly wanted to say "yea like her hoe mom right? So glad you know your daughter will turn out to be a hoe at such a young age"but of I didnt say that. 
How would you have responded? I laughed it off and was like yea let her teach me.