Hi Joanna,
He didn’t try to finalize the dinner date for Sunday. A guy who doesn’t finalize a date is often showing signs of disinterest or waning interest.
Being that the first date that you had with him earlier this week went well, he may make another attempt to set up a date with you fairly soon.
If he sets those date plans up but doesn’t follow through with the date, that would be your indication that he has definitively lost interest.