The elytra does not work, maps take a long time to show there pictures, blocks dissapear when I place them, items in my inventory dissapear, game is very slow

What I expected to happen was...:
the elytra would let me fly, maps would be instant, blocks and items would stay where they should, game would be normal

What actually happened was...:
The elytra does not work, maps take a long time to show there pictures, blocks dissapear when I place them, items in my inventory dissapear, game is very slow