When I create a new doc, the cursor disappears when on the canvas and the paint brush doesn't paint when I start to draw on it. The drawing only appears when I play with the brush sizes or click on anything in the side panels. The cursor only appears on the side panels but not on the canvas.
Your display driver is broken. Enable the Angle Renderer: https://docs.krita.org/KritaFAQ#Krita_starts_with_a_black_or_blank_canvas_and_nothing_changes_when_you_try_to_draw.2Fshows_a_black_or_blank_screen_on_my_Windows_system_with_an_Intel_GPU
*** This bug has been marked as a duplicate of bug 360601 ***