This is amazingly cathartic. Getting rid of things that no longer bring you joy or are needed in any way can lift a weight off your shoulders. Recycling old papers, bank statements, messages and the like, helps keep surfaces cleaner and files thinner. This makes it easier to find the important things.
Take a day or two and rid yourself of any mountains you have. Then do it daily and again weekly. It’s like mowing your lawn or showering, it’s often better with greater frequency, not less.
Then when you have less stuff, it’s easier to organise those papers, files, toys, gadgets or general items. Be brutal with this concept. Refuse to let any random item have space in your life. Bin it, recycle, give away or cherish, but with a specific place of its own. Life will get better.