In theory, you should be able to install ASIO4ALL without uninstalling the Focusrite driver and just select ASIO4ALL in Cubase’s audio properties. In practice, it’s impossible to rule out that the Focusrite driver would not create conflicts, so I would eliminate it just as a precaution. Or you could try installing ASIO4ALL, de-selecting the Focusrite driver and selecting ASIO4ALL in Cubase’s audio properties and see if it works. If it doesn’t, remove the Focusrite driver because it’s likely creating a conflict.