Grav needs at least PHP 7.1.3 to run error. Although the actual version is 7.3

Dear members,

I entered the admin dashboard and saw the big button saying that my Grav was outdated and needed updating. So in my enthusiasm I didn’t think and pressed the button to update. First I got the message “Argument 1 passed to Grav\Common\Processors\DebuggerAssetsProcessor::process() must be an instance of Psr\Http\Message\ServerRequestInterface, none given, called in /home/dieterto/public_html/system/src/Grav/Common/Grav.php on line 132” and while looking at that line 132 offline I got in the dashboard the next message “You are running PHP 7.0.33, but Grav needs at least PHP 7.1.3 to run.” and then I was thrown out of the dashboard and I got the PHP message in a white screen. My website isn’t visible anymore. I know, I should have thought about that before (though a little warning before pressing the button would have been a good idea). So, I went to my cpanel and updated PHP successfully to 7.3. In Firefox it resulted in a blank screen and in Chrome in a page not accessible Error 500 message. I tried then out different things as described in Grav online documentation: I created an info.php file to see if php 7.3 was installed (Cpanel said already it was) and yes depending on what .htaccess was used a long page appeared with all the info about the php installation (I printed this in 21 pages in pdf) and it is 7.3. I put the word test in the first line of .htaccess to check whether php can detect the file and yes I get, as expected, the longer error message which is proof that .htaccess is being detected. I out commented and tried other changes to .htaccess as advised here: Not all of them though as I don’t want to mess up more or because I can’t do it (like restart the Apache server of my hosting company).
Anybody an idea what I could do? I have a back-up of the users folder (from before updating). So, I’m thinking of replacing all folders and adding the files and folders of the latest grav-v1.6.23 except the users folder. However, I’m afraid that this might even make it worse, if some other files than those in the users folder have an influence on the content (which I don’t know; I find Grav’s structure rather confusing, although I have found mostly everything to change my website under the users folder).
You can answer after Easter (I hope) and I wish you many Easter eggs brought to you by the Easter bunny…

Meanwhile anyboddy there who could help me?

As there is nothing coming from this community I have changed my website deveopment and am now happily using Sitemagic CMS Simple, easy, free, many functions, nice templates, can be hosted for free there, can be downloaded or can be hosted on your webhost site or your own server. Site created within less than an hour. Goodbye Grav!