Xcode 9.3

Hi all, Need your help with this so annoying issue in xcode. All this software which is supposed to be a fast one does is to lag after a few minutes of simple code writing. I started to learn Swift with some courses and I’m just doing some exercises to build required skill set, so I’m new and don’t know what to do after I have tried some “solutions”: fresh new download and reinstall, downgraded to a previous version which worked fine last year, complete macOS reinstall... none of these seemed to work, I’ m going to be disappointed Any tips will be very appreciated, thanks in advance. Hardware: MBP 13” mi-2012, i5, 500gb HDD, 8gb RAM, lates High Sierra