You can save yourself a lot of time and hassle by learning a few of the Photoshop keyboard shortcuts. Here’s a list of keyboard shortcuts that you will probably frequently use.
Cmd/Ctrl and Z - undo the last step
B - brush, selects the brush tool
[ - decrease brush size/diameter
] – increase brush size/diameter
Shift [ - make brush edge softer
Shift ] – make brush edge harder
Z – zoom in
Z and Option/Alt – zoom out
Cmd/Ctrl and 0 (zero) – fit image on screen
Cmd/Ctrl and + zoom in
Cmd/Ctrl and - zoom out
V – Move Tool
Space Bar – toggles the Hand tool on for moving around a large image
Tab – hides the panels
Shift & Tab – hides panels but leaves Tool bar visible
Cmd/Ctrl R – hide or show rulers