Objects and some part of terrain gets invisible if I move the player

Now the thing is

I have cylinder as my player in my game and i added a main camera in him with correct coordinates

I used the demo scene provided by the
Free asset called Fantasy Environment in that i deployed my player and when I move my player even a single inch something in my world goes invisible
It’s still there because I get stuck to it’s box collider and also mesh collider for houses but I simply see through them they are invisible and if I move a little again they will be visible again move again invisible no code added at all to game other than character and mouse controller

The only thing is changed that i increased the scale (size ) of a town in it to 1.5 for all three axis x,y,z.

And more importantly this is happening with terrain as well as I move some part goes invisible some visible and again move invisible again move visible

Please help me I am learning the unity all settings on default and nothing changed its the Built in rendering pipeline and all the assets are for built in as well I am not using any mismatch objects or assets