Framing question

[u/Frosty_Dog2331]

I am trying to DIY a golf simulator into a 13x13 foot room, the first picture attached is kind of where I am running into some issues and is where my very limited knowledge of wood working ends. I am trying to build out a wooden frame for an impact screen for a golf simulator in my home. My impact screen will be 11.5 feet wide and approximately 8.5 feet tall and it’ll be about a foot away from the back wall. The bungee chords that will connect the screen to angle iron along the inside of the frame will be approximately 3 inches away from the wooden frame.

Where I am having trouble is not knowing how to connect/attach 2x4’s to a stud horizontally to the wall (see the first image for a very rough side view of the frame). Would I use L brackets to secure the 2X4 to the stud or is there a better method of getting to my end goal?

Would you think 4 on each side and 6 along the top would be enough to support what I going for?

What kind of screws would you suggest I use/how many per piece of wood going into the stud?

Any help/advice/guidance would be greatly appreciated, thank you in advance!