You say “he has my heart” in Spanish like this:
"él tiene mi corazón"
This could have two meanings attached to it – either he literally has your heart in his possession, which means you can’t possibly be the one making the statement, or you are in love with him.
If you want to learn how to say this out loud, you can actually use the reader on Google translate in order to hear these words spoken out loud.
You can hear these words spoken right here.
It can take a bit of practice to get the pronunciation right, but just keep at it. If you want to make sure you have got it right, ask someone who speaks Spanish fluently to translate what you’re saying.
Most importantly, though, you should always keep learning and trying to interact with Spanish-speakers- it’s the only way to become a fluent speaker yourself.