Aperture-priority and shutter-priority modes are fine when you have limited time to compose your shot eg you're shooting something that's moving, and the light might be changing.
But for many landscapes, you've got time to compose the shot, including choosing aperture/shutter speed/ISO. So I'd suggest that you go straight to M(anual) mode. It takes a little while to get used to, and you do need to review the shots as you take them (which you should probably do anyhow), but you're then not constrained by the camera's light meter.
From the photos, it looks like you have the Sony RX100M2, so it has a perfectly good manual mode.
Other things for later (or now)
- get used to looking at the histogram
- get a tripod if you want to shoot waterfalls (you may have one already)
- if you want to shoot long shutter speeds on waterfalls, you may need a filter (this could be why your shots were overexposed?) - Circular polarisers are excellent, unfortunately the RX100M2 has no built in ND (neutral density) filter - the M3 does.
phan_TOM wrote:Most important is not to get too caught up on all the technical crap and just remember to have fun
...though it's not much fun when you get home and your photos all have technical faults when you look at them on a big screen!