Game Slowing down

i develope a 3d game , its slowing down after few minutes and taking almost 500mb memory ,
Please suggest me for optimization or solution,
Thank You

maybe you can use memory tool to see where the memory increase:

And can u tell me the possible reasons of slowing down game speed like animation speed and physics falling down speed…i mean everything is slow if i leave game alone .means while i am not playing

This is based on your project to determine a large possibility is a memory leak, not freeing up unused memory.

how can i determine , memory leaking or not ?? and how can it be fix

you can learn how to debug your project first, then try to fix it.
https://docs.cocos.com/creator/manual/en/editor/preview/?q=

Have same problem