Hi Shai,
And thanks for the feedbacks. The purpose of the application is to spot dirts in the city (camera icon) which are geolocated. Then when they have been cleaned the user who spotted them receives a notification per email (email address to be set up through the letter icon which opens a new form). The user can see statistics about dirts in their vicinity (cloud icon), and can see where the dirts are around them (radar icon which opens a native map).
Regarding the material icons, I used for example :
FontImage.setMaterialIcon(takePicButton, FontImage.MATERIAL_ADD_A_PHOTO);
but I may have messed up with the style so that they don't look material anymore!
Indeed I first removed the toolbar but now I feel like it would be better to group all my secondary action buttons into a sandwich menu in this toolbar. So I will definitely use the methods you suggested. Thanks for pointing them out.