Sorry, maybe this is more of a computer question,
my MacBook is just 8GB ram, and I can’t install more ram because on this model (2012 MacBook Pro retina) memory is soldered in motherboard.
Is there a way to utilize part of ssd to be used for virtual memory somehow ?
Your SSD already is being used for virtual memory. When your physical memory is insufficient for your needs, memory is paged out to your SSD. In other words, while you have 8 GB of physical memory, you have an enormous amount of virtual memory because that will employ your SSD. If you’re seeing performance problems, that’s simply because access to your SSD, as is to be expected, is slower than your RAM. Unfortunately, there is no substitute for increasing the amount of RAM.