#16 (the little girl) would be a winner had you focused on her EYE instead of her hair.
I don’t think focus is the problem. Her right eye eyelashes are pretty good. Depth of field is really shallow though. However, her nose seems to be in reasonable focus and hair that seems to be just in front of her ear is in focus, so her eye must also be in focus. She does have dark green eyes and her pupils remind me of a cat! They appear to be oval instead of round. Here is a somewhat edited version of your photo. I removed a number of stray hairs, tried to put some colour into the left side of her face and sharpened her right eye (probably too much). Click the photo to see the large size.
Let us know what you think of my edit and I will take it down and get my space back.
The worst photo might be the child with camera, #15, where the sharpest part of the photo seems to be the lint on her sleeves.
Of the people photos, I’m drawn to #8 the most. You have enough depth of field, but not too much, exposure is good, they are in relatively the same plane so their size is not distorted. Their expressions are great too. The most notable problem with it is the white has blown out so his collar has blended into the shoulder and her dress details are lost. If there is a raw file you can get that detail back through post processing.
I like the alley scene #2 in places. The yellow building at the end is a bit blown out but I like the composition and nearly in focus wall on the right.
#1, I feel is leaning to the right and I don’t know where I am supposed to be looking, or what I am supposed to be looking at. Getting low and using one of those bollards as a main foreground element may have helped. Keeping the camera level side to side and front to back prevents some distortion caused by perspective.
#3, has that same “I was there, I took a photo” feel that #1 has. Both foreground boats are partly out of the frame. There is a lot of empty sky. The horizon cuts through the middle of the photo. It would probably have been better to back up a step or two and get the rest of the boat tied with yellow rope. Getting a little lower so the tallest mast is just in the photo might have helped too. All easy to say while sitting here exercising 20-20 hindsight.
#4, has the camera tilted up. Sometimes that is unavoidable. The effect can be removed with software if you don’t have a special lens. Fixing the tilt takes a bit off the sides of your photo. Once again, there does not seem to be a focal point.
#5, does nothing for me. It is a geometric shape and some leaves.
#6, is almost there. Someone has a pool on the roof. The view is from up high. The courtyard has lines strung above it to keep birds away. The square has a fountain or monument with a moat. This would be a better photo if the lens were shorter and pointed even more down, so the whole square was in view but keeping the view down the street. Sometimes you can take 2 or 3 photos with the same settings and focus then stitch them together. It’s easier with a wider lens and one photo.
#7, is kind of neat. Shooting across the rooftops has been done before. Your photo has distortion because the camera was not level.
And so it goes …
The question is, why are you taking the photos? As vacation photos go, they are pretty reasonable. Even as stock, some are pretty reasonable. For portraits, most would benefit from a longer lens. For landscapes, some would benefit from a wider lens or larger format sensor, or both. Keeping the camera level or a tilt-shift lens would help. Tilt-shift lenses are expensive. Unless you would use it a lot, software correction and trying to keep the camera level are more attractive options. Taking time to figure out why you are taking the photo, what do you want the viewer to see/feel, will help.