Okay, I found where the problem was. wp-config used UTF-8. I had to changed that to UTF-8 without BOM. After doing this, I could finally log into dashboard of my site. I was 100% sure this file was right, but I overwrote it in Friday. So it was my bad. Case closed.
Okay, I updated it once again manually to 5.3, but with no effect. All I get is the message “Cookies are blocked”. What to do now? I don’t have SSL certificate and I can’t use certbot.
I cannot increase those times/sizes. It’s already at max values.
