This is a good starting point for every beginner, who wants to learn more about the interface of Gravit Designer.
Menu Bar is the backbone of any design editor. In Gravit Designer, it is located on the top of the document and contains five menus. Learn more about them clicking on the links below.
Frankly saying, you cannot do anything without using tools. To modify an object you need to select it first with the selection tools. To create a new one, you would need either drawing or shape tools.
Finally, you can alter your objects and create more attractive designs with other tools in Gravit Designer, that do not fall at any of the above-mentioned categories.
Understanding the capabilities of each tool would help you to streamline your workflow. Stop guessing which tool to use, learn more about each of them here.