I couldn't write a diary yesterday cuz it hasd been a while since I got together with my high school firiends.

We talked passionately about our future life and our marriage.

This sounds like you are planning to definitely marry one or more of your high school friends. Maybe you meant your future marriages?

The conversation was so heatedintense that we were talkinged in the parking lot of a family restaurant until 6:00 in the morning.

A "heated" conversation is one in which the speakers become passionate or excited and perhaps start to debate/argue. This is also more often used for debates and arguments.

An intense conversation is one in which the speakers are deeply involved in it and may last hours.

I couldn't write a diary yesterday cuz it has been a while since I got together with my high school firiends.

The conversation was so heatedinteresting that we were talkinged in the parking lot of a family restaurant until 6:00 in the morning.

"Heated" usually means that there's an argument.

I feelt that friends with whom I could talk seriously like this weare really important. They are my best friends.

I want to get together with them again and again when I come back from my studying abroad.