Is there anything like world war(big wars) in animal kingdom or only humans are so silly?

If you imagine the sort of planning involved in anything more than a brief tumble, it would require communication and coordination far beyond the abilities of any non-human species. There will be a lot of examples in nature (chimps, ants) of group attacks, but these will be local and simple (not multi-phased and scheduled). There will also be examples where chemical communication can trigger group attacks (think of wasps), but even this is down to a common 'hard wired' response from the animals rather than the product of intelligent actions.

yes

many animals and insects are territorial

if another animal (the same kind most times) enters there territory (country) they fight the invaders - that sounds like war to me

no official wars in other animals

No animals only kill to survive,Humans just kill for the sake of it my friend.

yes its called the food chain..humans are part of it....except vegans...their just statistics