I had a similar problem, try changing the mouse scroll speed through either control panel or settings app, it allows you to set how many pages scroll relative to moving the mouse scroll wheel.

Search queries beginning with a number redirects to the forums main web page which is https://forums.opera.com/ for example, if I make a search for "64 bits", I will be directed to the main page rather than being shown the search results.

Thanks for your response, I hope the web installer issue get solved quickly, so we can install the appropriate version more easily.

Does Opera web browser have a 64-bit version for Windows in the stable channel, if so, how can I download it ?
Is there an option in the web installer to choose the 64-bit version ?