hey @sedatcakir, sorry you’re running up against performance issues 
I’ve been there before too and it’s stressful.
I’ve detailed out a list of 5 things you can do to reduce memory usage (this is based on Figma’s own documentation and suggestions) in a reply elsewhere in the forum that you may be interested in checking out.
If you don’t mind me asking, I’m curious why you’re working out of one big file rather than splitting things up across smaller files?