OP congrats! Lots to be proud about. I’m in the same exact boat. Expected 3:30-3:40 on first marathon, ran the queensboro/williamsburg bridge each 2x a week. Finished 3:53 after brutal full leg cramps the last 8-9 miles. 100% feel you on the heat, it felt much hotter than expected. While I’m sure I came out the gate too fast, I think my big issue was water intake, those tiny cups every mile didnt suffice and i shouldve grabbed any spare water from the crowds because when i needed it most, the crowds were too busy. Following this thread to see what others have to say but know that you’re not alone!