Hi @ancapavel2017,
Why not just contact the author of purchased theme, as adviced by @SpaceStockFootage? I’m pretty sure they may have an idea on how to handle this issue 
Anything we can suggest is related to WordPress core functions only, like @AlekseyZhdanov reply. Also are all the pages available in “Pages” section on your blog dashboard? Can you preview them by clicking “View” link underneath page name?
Thanks,
Luca