It allways pop up

It allways pop up " nothing found" or "404 nothing found" or " post a comment" and when I click on the search button, the store side pops up. showing my store site and difficul to customize.The only thing I have been able to do on my site is adding ( with no options possibilities in the gallery such as video, schicth items etc.) Items in the store. No functional options are: Paypal, Mutilangual, Widgets, Some of the Header and Footer widgets are taken back or have disappeared. Cannot customize the Header or footer- everything just hangs. Cannot checkout and item in the store.