@meyap Hello. I see that you posted similar complaint in 2022 regarding downloads. For two years you have had this problem, which suggests to me that it isn't the browser but could be your system, network, site or perhaps the files themselves that could be causing the issue. I and many others do not have any issues regarding this in Opera.
Try an alternative browser is always an option.
If your browser crashes during download, it is likely the cache/temporary files wouldn't be stored properly and could explain why they aren't appearing in your list. This is quite typical of applications that crash.
I would like to help people that experiencing issues but only if they remain civilized. There is not need for foul language - you risk being ignored for just being disruptive.