@yaguznal i dunno if this will help..
Go to opera://flags/
Enable this flag called - (Memory coordinator) it suppost to give the browser control of manage 'n memory instead of the operating system..
then later on perhaps this one..
try this Flag called - (Strict site isolation) *uses more ram probaly..
it is meant to make browser more stable and secure.. By separate 'n - every tab - plug 'n - extension - into its own process.. *may use more ram..