Different things work for different people. Starting at one corner and working across until everything is sorted out can work if you have time and the resolve, but so can setting aside time to regularly reduce a mountain to a molehill. You know what has and hasn't worked for you in the past. However, your current circumstances are something you have not experienced before so the old ways might not be applicable.
>For example, I have 13,000 photos on my phone and 1096 unread emails, how should I tackle this? Are there any apps that can help?
The images can wait. Consider ensuring they are backed up if you think they are important. Emails though - are they mostly things you are subscribed to, or are there important things in there?
Make a folder called Important2023 or similar. Work back through the last 7 days of emails. Delete them or answer them. Unsubscribe if you need to before deleting. If ONE thing (probably) is important, move it to the folder.
Every day deal with any new emails. This might be deleting and unsubscribing. Work back through another week.
And so on, until you reach a don't care about this long ago state and just leave the backlog there until enough time has passed that you can just delete it all. You might need an ImportantBefore2023 folder.
If you are not into folders, you just star/flag the rare important email and periodically cull them.
>I find myself cleaning my home every single day, I become obsessed with it being tidy and feel claustrophobic if I think it's messy. Is there any way I can teach myself to relax and leave it for a couple of days? (obviously I'll clean toilet and kitchen sides every day).
It's good of you to do the weekly clean every day. You don't need to. It can be done weekly.
That doesn't mean that there aren't things that need to be cleaned daily, as you identify. There's also the 15 minute tidy you can do at a set time every day that stops clutter building up.
>Paperwork for car, insurance documents etc are not organised at all.
Assemble paperclips, or similar, and a box, recycling bin and a sack. Work backwards through the pile(s) making stacks that you clip together and keep for now, recycle, or put in the sack for confidential disposal/shredding because it is sensitive. Keep going. It doesn't take long. You can organise the clipped documents in whatever way makes sense in the box. As any other paperwork arrives it goes with the correct clip in the box or speedily to shred/recycle.
As I said, different things work for different people. If you are anxious, start with something that gives visible results.
Edit: tidied a couple of words.