I don't know how to increase Ram for default Opera, maybe there is something here.
But:Chek TaskManager - Shift+Esc | Opera Menu - Developer Check on a Clean Profile [*] Install TabUnloader from Addons.Opera.com Install Anti Mining lists from FilterLists.com On Opera's AdBlocker [Settings] On uBlock - Addons.Opera.com
[*] New Profile, rename yours, Tip's info.
"Off Topic Tip"
Follow the Signature's Backup | Reset link.
Take the opportunity to start a Backup plan and even create a Template Profile.