Delay in controls

when ever I go to Minecraft and start a world in creative mode and try to double press the space bar it won't put me in fly mode until I do it multiple times till it works. the same applies to when I try to exit fly mode I have to hit the space bar multiple times to make it work. Also when I try to do 2 functions at once the game lags for a few seconds. For example, when I try to fly in creative mode and destroy a block the game lags for a few seconds. This happens when chunks try to load when I'm near it.