WP 4.0 Menu limit

Is there a way to increase wp_nav_menu limit, because in my site it show only 15 menu, and i can’t add more pages.
I have tried everything that other people have said in other forum-post of increase memory limit, change suoshin, max vars and other things. And nothing have helped me.
This driving me crazy, so please, can anyone tell me what to do next?
And I’ve also another issue that every time i try to save my nav-menu the page wont reload. It hangs itself up. And I always have to reload it myself. And when I do the menu have not been saved… And then I try to start over again… but the same problem remains!
And it not working to tick the box ‘automatically add pages at top level in this menu’.
So I’m running out of options!
So please help?
Thanks,
Linda