Upgrading 3.3.13 to 3.3.14

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One of the changes must be the culprit.

I re-installed 3.3.14, the same result again: only 404 pages instead of content
Then I switched the PHP versions in cPanel. The last version that makes page content in 3.3.14 is PHP 5.6.
PHP 7.0, 7.1 and 7.2 do not work with my site.

I let 3.3.14 be installed now, but the server is on PHP 5.6.

What still irritates me, is the english GUI, even on PHP 5.6. I always had a german GUI before.

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