Hey Hive account@motey, If you are writing under the steemSTEM tag, please credit all your images properly and use only those images which are free to use( Creative Commons, Public domain). Also, where are the references to back your claim?

Concrete building will start to collapse as oxygen helps to bind all concrete structures
As oxygen constitutes 45% of the Earth's crust ,The oceans and other water bodies will start evaporating into space. There will be no water bodies left on earth that means no phytoplanktons , fishes and other sea creatures

If you are writing a science post, please use a logical step-by-step argument with proper referencing.