@lubos This post and this other post Slow Performance sound like the same problem. Both are using Windows 10 core i5 computers. I am wondering if its not some windows update on Windows 10 that is messing around with Manager. The other poster was on quite an old version of Manager when the problem started, so its not an issue with a version of Manager. But both problems have occurred quite recently and suddenly, so that may point to a windows 10 update.
I would suggest you combine the two posts and see if both OP’s can help narrow down when the problem started, so we can eliminate some windows 10 update. I suspect its either an IE update in W10 or something to do with .net framework update.
I can rule out the Anti Virus because I can see this OP is using Avira which is what I use as well.
One suggestion that I can offer is to do a system restore to say one month ago. If this fixes the issue, its likely some windows update that is causing the problem