How can I eliminate the null parallel to the ground plane in 5.8GHz PIFA design?

I am designing a 5.8GHz PIFA. That means the F antenna is in the same plane with the ground plane. And the substrate is FR4 (DR=4.3). Since the groundplane length is λ/4.

How can I eliminate the null parallel to the ground plane?

The output impedance is 50+30j ohm. Should I use LC matching or microstrip matching?

Of course, you should consider microstrip matching.

you should try to put another parazitic patch above the F
about 2-5mm high.