Create a connection between the house and the garage

Hello everyone,

I have a question regarding the mentioned subject.

We have built a prefab house using timber frame construction and a double garage in solid construction at a distance of 1.50 m.

Now I would like to connect the house with the garage afterwards, for example via a corridor.
For this, an F30 door would have to be installed in the timber frame, and a door would also have to be installed in the garage. My idea is as follows (see attachment):
Marked in red are the 2 new doors and the masonry.

Do you think this is possible and do you know roughly what costs I should expect?

Do you have any other ideas?

Thanks and best regards

Is the top edge of the finished floor at the same height in both buildings?

About 20 cm difference. But that should be solvable with a step.

Normally, it should be enough to install the F30 door in the garage. That is not a problem. The only thing that worries me is whether I can subsequently install a door (e.g. insulated room door or terrace door with a lock) in the exterior wall of our prefab house.