Installing AMD & Intel dual graphics

The Intel graphics driver is built-in in Ubuntu, so you don't need to install an additional driver for the Intel graphics. It is also OK to have the proprietary AMD graphics driver and the built-in Intel graphics driver installed at the same time.

Whatever you did to install an unnecessary additional Intel graphics driver is what caused your low-graphics mode error message. To fix the problem, uninstall the unnecessary additional Intel graphics driver. If you can't remember the name of the graphics driver to uninstall it, you can find it by checking in the History tab in the Ubuntu Software Center, and if you installed it from the terminal you can find it by checking your terminal history using the history command.