Hello Felipe,
Does the black bar only appears in your homepage? Did you see it in other pages as well? It could be that there are some broken html added in the homepage that resulted to this issue. I inspected your homepage and I could see that you have this:
Please make sure that all your contents is a valid html with correct syntax. Broken code or unclosed tags could potentially messed up the layout. This could also be caused by a 3rd party plugin. You could try testing for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it’s fixed, you’ll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
Please let us know how it goes.