Menue craps my site oftenly

What’s the problem with this theme? Why header menue does not save, if I change it? Why category menue jumps to main menue so frequently? Why all menues do not save, if I change any of them, and instead of this, they just give several bugs? Are you going to set persistent problems with menue issues decisively? This theme has repeatedly broken my site and each time, so I have had to reset or rebuild pages and menues, and occasioanally I ve had to restore the whole site by previous back-ups! I’ve several times deleted third party pro-plugins to exclude any probably affects, but it did not matter any way. I so regret buying this ugly theme!!!