A6000 focus problem; noisy and blurry images

[mirperei]

Hello everyone! 
so, after much searching for an answer I guess I need to show (to someone who understands what I’m talking about) examples of my problem. 
the first images were shot with the kit lens (16-50) or the 18-200 OSS SONY lens (great lens!) a few years ago and had no editing. 
they were amazing! I could see them razor sharp in the PC and I’ve printed quite a lot of them (biz sizes as well). 
but lately (end of last year, and 2020) I’ve been seeing that the camera has much more difficulty to focus (it takes wayyy more time to focus) and most of the times doesn’t even focus at all. 
I used mainly P or SCN modes but now that I got a bit more to learn about photography I’ve been trying to get into M mode. And also bought a prime lens (Sigma 30mm f1.4). and the problem persists! Even with the sigma lens (which has the reputation of being perfect sharp) I see lots of noise and just not a good sharp image, not in the viewfinder and even less in my new Mac... 

I don’t know what to do. Wanted to buy a new one but I really loved my a6000 and don’t want to just dismiss it because it’s “outdated”. 
 

ah! I’ve upgraded the firmware and have initialised it many times... still, some photos are ok but not great and most of them do not focus at all! 
 

Suggestions? How can I be sure it’s defective?

thanks!!! 
 

Dropbox link to photo comparison: https://www.dropbox.com/sh/u6mhu47ltmoecic/AADDNuVFUOUX_60RLm-xIetla?dl=0

Edited January 29, 2020 by mirperei

[mirperei]

I also realised now that when using a higher f stop (with my sigma 35mm) the focus in the camera is really struggling - going back and forth back and forth... ? 

and sometimes the viewfinder (but also the small view for your eye - don’t know what’s its name) goes all black. I have to switch off and on the camera to have it back. 

[Therado]

I've also noticed my images are really crappy and full of noise even at low ISOs like 100 - 500. It's really bothers me cz I'm starting to take on client work. 

 

Have you had your camera serviced recently?

 

I'm thinking my sensor might be dirty but can't be certain.

[Pieter]

Doesn't sound like a dirty sensor, sounds like wrong settings. Can you post the exposure values of one of your bad shots?