How to restore my custom size from 500% back to 100%?

Yes, it was very stupid idea. But I was tempted to. Anyway, I want it to return back to normal but the size is too big for me to return everything back, I tried Googling answers on my phone and nothing was any help.
People keep on saying that I should probably put my computer in safe mode and then do it from there. Problem was… Safe mode also had the very big font. My computer runs at 1366x768.
I also tried restoring. But I have no idea how to do that. Does anyone know how to do this? If you could make a video viewable on iPhone… Thank you from my heart!

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