Good Riddles

Question: I get dirty in about 5 days but it takes half an hour to clean me. It takes a long time for me to be tall but I can be short in about 2 seconds what am I ?

Question: why is six scared of nine

Question: can you make an equation by using only the no.-4,4,4,4 whose answer will be 20.

Question: What goes up white and comes down yellow?

Question: What's a plate when it has three spoons in it?