Front derailleur wont shift to biggest ring. Cable is as taut as i can get it.

Bought a brand new Shimano 105 2x12 speed groupset and put it on my allround bike frame. Went for a ride two days ago and had lots of chain rub while on the biggest front ring and the middle of the cassette and downward. Thought it was an easy fix but now I can't get the derailleur to shift at all.

I dont know if there's an issue with it since I have to use the H limit screw to get the derailleur to move outward. If i screw it all the way in the derailleur is almost in line and I can almost get it to shift. Tightening the cable seems to do nothing.

What I've done:

Re-fitted the derailleur and double checked the alignment

Tried different ways of getting the cable super taut

Ruined my derailleur cable

Played around with the limit screws.

Followed all the steps of an installation video I've found online.

Feels like I'm going crazy as I can't find the solution. Does anyone have any clue what I should do?

Don't know how well i can explain this since English isn't my first language but the top part of the derailleur is made to "flap" when the cable is tightened. In videos I've seen this part lay parallell to the ground but mine seems to want to flap around unless i tighten the H screw before I install the cable. Is it supposed to be like this?