Help with Bottom bracket replacement on SCOTT MTB?

You don't mention whether you have removed the drive side crankarm. In order to change the bottom bracket, the cranks have to be removed on both sides. The square hole in the end of your bottom bracket tool is probably for use with a 3/8 or 1/2" ratchet . A hex key will never generate enough leverage to remove the bottom bracket cups, you need to buy or borrow the correct tool to do the job, it is pretty easy to damage the tool or the bottom bracket cups so badly that you won't be able to remove them.