I've had my flair for 2 weeks, but my grinder didn't go fine enough for espresso

So I ordered a c40, and its really good for any brew method, I love it

So, for espresso, I don't know what i'm doing wrong, I've pulled a lot of shots, all of them were sour

At this point, i'm not even sure what to do, should I sell it and buy a Gaggia? Or do I spend time learning?

I've wasted a lot of good coffee on this :(

What I'm doing:

1. Preheat
2. Measure my coffee(16g, i've also tried more but the portafilter is way too small)
3. Grind at 7-12 clicks
4. Dump the pre heating water and pre heat again while I put the coffee in the portafilter
5. Put shower screen on
6. Dump pre heating water
7. 20 secs pre infusion
8. Press for 30 secs, and whatever grind size I use, it barely requires any pressure

Any help would be very appreciated