The problem is when i start the game my character going to bottom . But that shouldn’t like be that.İ added tile map collider 2d but somehow that’s not effect my platform . how can i solve this problem ?
does your character have a rigidbody / collider, as well as the both tile map and character and player having colliders not set to trigger. Also check collision matrix in player settings.
… and make sure your player is on the same tilemap layer as the ground. 
Have you selected the collider type for those tile assets as per the manual for TilemapCollider2D? Adding a TilemapCollider2D won’t automatically give you collisions as it wouldn’t know which ones need to have them and which ones don’t.
Beyond that, click on the TilemapCollider2D, look at the inspector, open the “Info” roll-out and look at the shape count shown. If it’s zero then you’ve not got any tiles with a collider type set. It should also drawn the colliders when you select it.