More information is needed before someone can help you:
https://www.zotero.org/support/reporting_problems

I apologize if I wasn't clear. I wasn't suggesting that you provide a report ID number but asking for much more detailed description of your problem. This is particularly important because you seem to have asked two, perhaps, related questions.

Given your earlier question about syncing and attachments, I am unsure of what is the exact problem or question. The experts cannot see your screen or what you are doing or the steps you are taking to accomplish your task. I an not one of the experts but I think that your questions are unanswerable until you provide more details. Please describe exactly what you are trying to achieve.

I can think of more than one way that a list of attachments will "pop-up". Is this related to syncing?

the second problem: for the notices as well as for the attachments there is the column "created" and "changed" (i tranlsate from german). when i work on the attachment an save it again, the date of "changed" should change, no? but it does not

To collapse all items in the center pane ("hide the notices"), press the - (hyphen/minus) key on your keyboard. (Pressing the + key will expand all items)

For your second issue, I'll let Dan answer. I'm not sure if file attachment modification time in Zotero is determined by the file modification time or editing attachment metadata. If the former, I'm guessing that Zotero doesn't continuously check the modification time, so it may not update until you restart Zotero.

No, that's not going to happen, since the search query specifically matches the file attachment (or note).

i know that i can use the minus key, but i would like the items to be collapsed withou me having to collapse them all the time.

If you don't want child items, you just need to search in Title, Creator, Year mode, which doesn't match child items.

the second problem: for the notices as well as for the attachments there is the column "created" and "changed" (i tranlsate from german). when i work on the attachment an save it again, the date of "changed" should change, no? but it does not

The middle column shows the attachment item modification time, not the file modification time, which is shown in the right-hand pane (and updates when you switch away from the item and back).

In the right-hand pane you should see "Modified", which is the file modification time. If you edit the file, as long as the modification time of the file is actually changed by the program you're using, when you click away from the item and back it will show the current mod time.