Focus problem with my new EF 24 1.4 II USM

I everyone,

I just spent all my savings on a new EF 24 1.4 L II.

At home I discovered some sharpness issues. Since it is my first L prima lens, I want to know if the user (me) is the problem, or the lens.

I use it on my Canon 7D. I have an EF-S 15-85 and a EF 70-200 L f4. Both produced sharp images out of the box.

Okay, lets go, I shot this image first:

I felt that the chairs in the foreground were sharper than the focus area.
So I mounted the camera on my tripod and started testing...

First I did some shots on manual focus, to see if the lens at all has a problem:

Then I did the same on AF (center) One Shot Mode:

And this is unsharp!

Then, for the first time, I played around with the 7D´s AF micro adjust feature:

With the slider all to the right (+20), it became sharper. But maybe it would have been even sharper with +25 or +30, which is not possible.

Then I moved a couple of meters back, to see the effect at a longer focus distance:

Quite the same.

What should I do now?

Bring it back to the store? Or live with it @ MFA+20

Would you agree that the lens is heavily back-focused, bus doesnt has a focus-shift problem?

Are my tests fine, or do they need to be improved for a final judgement?

Kind regards,
Jan