Wrench button displays the popup menu below the header

Hello Guys,
I have some issues with the wrench button when logged in as admin.

When I click on the wrench button, the popup menu appears at the top, below the header. I am unable to use all the options available on the menu.

CSS inspection gives the below style. Is it a good idea to change the bottom and left to 0 px? I fear this break any other parts of the site later. I request anybody to help me fix it. I am not good at CSS.

css view

Thanks in advance