Can you tell reasons behind World War 1 and World War 2?

Yes: Both are the product of what had gone before in many ways. Both are essentially European & involve France & Germany. Britain & the British Empire & the USA & Russia are Allies. In both instances there is conflict on the High seas & in Africa & Asia & elsewhere, in WW2 there is also a major conflict with Japan in the Pacific. WW2 is, by & large, a product of WW1. WW1 is in some way concerned with both the Franco/Prussian war of 1870/71 & the Napoleonic wars. But it is a complicated process.....