I18N Special Pages

[pikku]

Hello!

I searched a lot in the posts, but I couldn't find anything about my problem: I can´t save existing or new special pages - it looks as if they fade out a little, and stop. It works with normal pages, though.

In debug mode I see following in frontend and backend as well:
Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; I18nNavigationItem has a deprecated constructor in /home/.sites/299/site5274122/web/plugins/i18n_navigation/frontend.class.php on line 349
And in frontend where the navi is:
Warning: count(): Parameter must be an array or an object that implements Countable in /home/.sites/299/site5274122/web/plugins/i18n_navigation/frontend.class.php on line 219

This points to i18n, but the problem appears only with special pages. And as the website worked once, i think the mistake is on my side.

My Browsers (FF) console tells my this for the backend, the moment I try to save a special site:
TypeError: data is null[Weitere Informationen] edit.php:692:1
<anonym>https://www.graswander.at/verwaltung/edit.php:692:1
n https://ajax.googleapis.com/ajax/libs/jq...js:2:14779
fireWith https://ajax.googleapis.com/ajax/libs/jq...js:2:15553
w https://ajax.googleapis.com/ajax/libs/jq...js:4:11393
d https://ajax.googleapis.com/ajax/libs/jq...js:4:17218

this is line 691 and 692 of edit.php:
//title validation empty
if (data['validation-failed'] === false){ //success

As I am no programmer this doesn´t help me - I hope some of you can.
I just tell you mey settings, an d what I changed to brake it:

I am working with GS 3.3.13 and following plugins:
AdminXML Plus V0.2 supposed to be 0.3
GS Custom Settings Version 0.5
DynPages Version 0.7.2
GZipIt.php deaktivated
I18N Base V3.3.1
I18N Gallery V2.2.1
I18N V3.3.1
I18N Search V2.13.1
I18N Special Pages Version 1.3.5
KCFinder File Manager V 2.2
migrate.php deaktivated
p01-contact V 1.1.4
I18N Special Pages extras V1.25

I developed this gs site some years ago and everything worked fine.
And on the frontend it still does! https://www.graswander.at

But I had to change the provider and with it I changed to php7.25 (from lower than 5.6) and https.
I installed the newest get simple and moved the site with the migrate plugin.
Than, as everything seemed to work I updated all the plugins, popping up - except GS custom settings, as it should not be higher than 0.5 with AdminXML 0.2. It says newest 0.2 is 0.3 actually, but I tried it with 0.62: AdminXML didn´t show up.
I would not really need AdminXML, but it didn´t seem to be the problem.
When I realised, the special pages do not save anymore, I tried to downgrade several plugins, deactivated gzip, which seemed to conflict. I changed my servers php to 7.1 and even 5.6. And I remove the only new things, a cookie disclaimer and a reimplementation of matomo(analytics).
What rights should the pages have? The folder and most pages had 755. just the special pages which show a list of other special pages had 644. I changed it to 755..
I allways had the very same problem.

hope you see the problem!?
thanx,
Oliver