When breaking a block I have to break it twice and then wait about 10 seconds for the item to drop. And it's really annoying because it wastes time before night.

Please provide a video of this occurring whilst the F3 debug screen is enabled.

I'm sure that this is a problem with the hardware. Can you show the debug screen's lag "graph"? (alt+f3 or shift+alt=+f3, the graph is in the bottom left corner) Or maybe you could show the operating system and current options (including particle effects and render distance), as these can have effects on the speed of your machine / Minecraft.