Hey Attila. If you want to get more out of the shots, a few pointers...
Depending on what software you use, try compressing the levels, especially from the right side (highlights) by sliding the right slider to the left (assuming photoshop but also works with Canon Digital Photo Professional DPP).
In your first shot I notice it was at f5.6 at 1/1600 ISO 200. You could've moved the aperture towards f/8 which would help get more sharpness at the expense of shutter speed.
My theory with shooting is to always get as sharp a shot as possible, then I work with RAW processing to bring the exposure up if I need to. Sometimes you need to shoot at f 4 or 5.6 but it's generally not the sweet spot for the lens, if at all possible go for f/8 or even f/11. I aim to keep my shutter speed at least at my focal length, so 1/300 in the case of your 75-300 if zoomed to the fullest. 1/400 for a 400mm etc. That's just a general rule though. I use aperture priority and watch the selected shutter speed.
Sharpening is always necessary if you shoot RAW, because the image is essentially bland/flat straight out of the camera.
If you're using Photoshop, Shadow-Highlight is very useful, and Unsharp mask as well. If you're using Canon's software you can still do a lot of these things but the settings are a bit different.
Here's a simple levels adjustment and 300% 0.6px sharpening for example:
