ed_f wrote:and yes, yesterday I saw a previously unknown login when adding index.php (if I remember correctly something blue on black) which was already filled out and gave way to the files gallery.
Not sure where you saw this, and kinda pointless to discuss if you can't find it again. If there was already a login, it was likely the Files Gallery link I gave to you, that is already installed on your X3 website. For example here:
https://www.architekturfoto.de/files/
Yes it has a login form of course, because it needs to be secure. If it's already filled, it means it's because you have logged in earlier or your password manager thinks it knows the password. Others can't login of course.
ed_f wrote:I uploaded it after your first answer, because after reading the instructions I didn't understand it's already there.
You mean you uploaded to your website root? In my first answer, I said "which should be installed in your /files dir relative to your X3 root", which correctly is
https://www.architekturfoto.de/files/ and is password protected.
ed_f wrote:however: today I do not find the gallery anymore. neither pointing to architekturfoto.de/x3/de/index.php
What "the gallery" are you looking for? What exactly are you expecting to find there? That url /x3/de/index.php is the same as just /x3/de/.
Besides, surely this has nothing to do with Files Gallery? Files Gallery is not installed there, and I have never told you to install Files Gallery anywhere (certainly not there).
At this point, you need to try to explain to me exactly what you are trying to do. Files Gallery is already installed here:
https://www.architekturfoto.de/files/
If you want/need to install it somewhere else, it should be installed in a NEW folder somewhere. Not overwriting into some /x3/de/ dir (what's the point of that)? Furthermore, you should NEVER need to access anything by writing "index.php" into your browser url.
For your info, these two urls are IDENTICAL:
architekturfoto.de/files/
architekturfoto.de/files/index.php
Never write "index.php" in browser. In your case, it's just causing you confusion. The index.php file is the file name that is automatically loaded (if it exists) when you access a dir (for example /files/). You can't have different "/x3/de/index.php" and "/x3/de/", they are the same thing. The only reason index.php doesn't load when directly accessed in that url, seems to be because you have some rewrite on server, but it really shouldn't matter because you won't find anything "different" by typing in "index.php".
At this point, I think you need to start from scratch:
1. Is there currently anything WRONG on your website? If so, what? Not being able to access "architekturfoto.de/x3/de/index.php" is not something wrong, because you aren't supposed to load "index.php" directly in url, and even if you could, it would only load the same dir page as the dir it's in anyway "architekturfoto.de/x3/de/".
2. When you/we have solved anything that's wrong, we could try to install Files Gallery. Until then, I don't even see what your post has to do with Files Gallery..