Safari not completing downloads

Hi, I've just updated my macOS to Sequoia version 15.0.1 and have a problem regarding safari - the problem is that most of the times when I download the file from web ( wetransfer, gmail, stock and etc.. does not matter ) the file itself adds a word "download" in the end, which I can't rename. For example - I've downloaded an .mp4 file and the word "download" is added in the end by itself. The file is useless. If I try to search the file from downloads arrow, as soon as I click the file it says: "Safari can't show the file ___ in the finder because the file has moved since you downloaded it" - But I have not moved anything. Anybody with the same issue?

[Re-Titled by Moderator]