stollen iphone

i fell asleep in my car with my window down and someone had the balls to reach in my window and take my phone in broad daylight in a park full of ppl where and event was going on and next to it there was ppl playing a baseball game when i woke up i noticed my phone was gone and 30 minutes later i got notification saying someone changed my passwords since my phone was unlocked wen they took it they had access to all my info n passwords now i cant get into my email because they changed my passwords and my phone number on my email and put there own i was able to go on my icloud n lock my phone by reporting int stollen but by then the damage was done idk what to do now my phone is now locked but the person had the adacitiy to try and sell me my phone back for 900 dollars and say he got it for 900 and act like he was mad at whoever he got it from which was a lie wen we were set to meet up i was able to locate my device but he must have seen that i was walking up to were he was at and got scared cause wen i got close to were my phone was showing it was at he turned off the phone now i cant track it but i lost access to my gmail and cant recover it what can i do now ?