If you have already cloned your chosen theme (Moove) then you've made a good start already.
But you probably need to give us a bit more detail about what you are trying to achieve - I presume by 'frontpage layouts of courses' you mean the course page itself? You also need in that case to bear in mind that the course page appearance can be altered drastically by the choice of course format used (eg 'grid' or 'tiles' look ver different from 'weeks' or 'collapsed topics').
But for the theme itself, the layout is generally created in the relevant layout file (see the theme config.php to determine which one), elements of which may reference renderers (such as the custommenu) and then gets passed to a template file to actually construct the hmtl. And of course that all gets styled by the scss.
So it all starts with what do you want to change - simple
css (in the scss files), basic html (in the templates), or more complex logic in the layout files.
I'm sure if you can come back with some specific questions about what exactly you want to change and how, there are people on the forum who can help you do what you need to do.
Richard