Bricking up the garage. Tips?

Hello,
we had a 9 x 4 m garage reduced to 7 x 4 m. Now the garage needs to be bricked up again. It’s already enough that I couldn’t do the demolition myself... Now, as the future builder, I at least want to brick a wall! However, I have never done this before...
In addition, a window and a door are to be installed.

The garage was built in 1981. Below it is a thick foundation with reinforcement and a frost skirt 80 cm deep. The walls are made of sand-lime brick (2DF). At the top there is a wall tie, which is currently hanging in the air on two sides due to the demolition. The ceiling consists of 4 m long aerated concrete slabs with steel reinforcement. These rest on the walls.
Now I want to brick up the front wall again, where the garage door was before and which has now been removed. Myself. In addition, a regular door and a window are to be installed.
In my mind, I was already planning to simply build the new wall at a right angle to the existing wall, so that it finishes flush under the aerated concrete slab at the top. A lintel above the door and window and that’s it. However, I was told that I should interlock the corners of the walls for stability. Also, the wall tie must be extended?

Maybe some of you can give me good tips on how to best start, which way is the right one, and whether I shouldn’t just let a mason do everything after all.

For clarification, I have attached photos. Both of the current state and the desired state.

Thanks in advance!

Best regards,
Manu

Glue it shut with Ytong and plaster it. It won't collapse anyway.

I would simply cut a joint every third layer there, and then build up the front with the same material and tie it in. But there is also the possibility to solve this with [mauerankern], although I would prefer a proper form-locked joint.

Seal it with Ytong and plaster it. It won't just collapse.

So you mean just at a right angle like I originally thought?

I would simply cut a key every third layer, and then build up the front with the same material and tie it in.
But there is also the possibility to solve it with wall anchors, but I would prefer a proper friction-locked keyed connection.

That's where it starts... "Cut a key every third layer." So basically, I start at the bottom in a right angle with the first two stones. Then I build in the third stone keyed into the already standing wall, and the next two again at a right angle to the existing wall, and so on?
Am I understanding it correctly that if I key in, I can save myself the wall anchor, and vice versa as well?

Thanks to you all!

Exactly. But the interlocking is the better option. And you can now mortise it without much effort.

- The same stone as the rest of the garage.
- As winnetou78 said, regularly integrate into the other walls.
- Pay attention to the horizontal barrier (I think you can also see this on the other walls).
- The first row is the most important, put in effort.
- For plastering, I would look for a mason (on the informal side, neighborhood help).

For the ring beam, I would say: dare to leave gaps, just brick it up.

A sheet metal edging should still be added to the roof.