open large files freezes

when opening large files it hangs, sometimes for ever, sometimes it opens eventually, mostly always i need to FORCE QUIT due to application not responding

could it be a memory issue on my machine? the spinning ball thing comes up sometimes, i have deleted all unnecessary files and folders and try not to open any other programs when working in DW

have used Recreate Site Cache to try to help, also Open New File helps and making sure the local site files folder is in order

but still, on my largest site with the most files and some very large ones, IT JUST FREEZES UP! however, when it does open eventually, i then close the file and it reopens again instantly, so its kind of like it found it and now it knows how to open it, but after restarting DW it loses it again!

would appreciate any tips!

DW 2018.2

mac osx high sierra

MacBook Pro (Retina, 15-inch, Late 2013)

2 GHz Intel Core i7

8 GB 1600 MHz DDR3