@leocg 100 MB out of 650 MB being used...is not a "(very) low amount of memory." That's literally 1/6 of the total that is simply not needed for most.
Of course....the other issue is all the "background Processes" that have to be on...unless it crashes your computer (or other programs.)....which means you have far less Memory to run stuff than you actually think.....and with Opera using most of that up.....That's what we're complaining about. Why are you a Moderator Answering these questions if you know nothing about how programs and computers run? Clearly, in order to run Opera, and play games at the same time, you need to massively upgrade you RAM, and available Memory to actually run things.