Help a beginner build a small wall

[blob]

Planning to convert this hole into a more standard opening. I plan to use steel studs as it is in the basement.



The shelves I will place inside on the left side are 20 cm deep. Therefore, I want the wall on the left to be the same dimension (20 cm) so that the wall just covers them.


The problem that arises is that I cannot place a stud on the other side as the opening would become too small overall.

How do I then attach the top plate(?) on the upper right side which connects to the right wall if there's no metal stud there?

Highly unclear why the last picture got finished as I made a mistake on it. Disregard the one at the bottom.

 

[parper]

Use a wooden stud there instead, you can mix metal and wood studs. It's only against the floor and possibly the lower part of the wall where moisture is a concern.

 

[anders07]

Don't quite understand the problem... you can place an angle against the wall on the opposite side and place a horizontal beam over it?

 

[blob]

All walls are essentially interior walls (row house). It's probably mostly towards the floor where there's a risk of moisture.

Angle, is it something that holds the wooden stud on the right side?

In other words, can I run wooden studs continuously except for the sill?