Hi and thanks for reaching out!
We'll add a learning mission later, but for now: you use left mouse button for most actions like selecting units, buildings, clicking buttons etc., and right mouse button for ordering units to move, attack, construct, repair and harvest. You can use scroll wheel or arrow keys to move camera, or you can move camera by moving mouse to borders of the screen. Let us know if any if this doesn't work for you.
Loading times are very quick for me, only 1-2 seconds. Other devices we've tested on have the same loading times, so we're not sure why they're so slow on your computer. What specs does it have?