Ayyyyy y'know what? This wasn't bad. Actually, for scribblehub standards, I'd argue it's pretty great lmao. Great usage of the senses--I could practically feel and smell the world. Honestly very fluid and great prose.
I have two critical points. As the others said, the main thing to think about is showing more and telling less. The second, while the world seems pretty sicc so far, I need more character work. The fact that there's only a single line of dialogue hurts my soul. This section really sells what I'm trying to get at:
The latest gift his father Johannes gifted him was a set of photos which he found in the old library. They were pictures of the city where the bunker was near, taken on a few hills that still existed. Finding this interesting Jonah visited the hills where the photos were taken from. When he reached those hills he compared the city with the pictures. While doing this he felt calm. He felt happy instead of sad because of what the city could have been. This intrigued Jonah. After this moment every day he would go up the hills and compare the pictures and the city.
"Jonah visited the hills where the photos were taken from" honestly should be a scene all on its own. We should see the journey and his first reaction to seeing the origin of the photos. Give some details that would speak of Jonah's character. Specific things that catch his eye.
"While doing this he felt calm". "He felt happy." This part is what we mean by telling less. And honestly, you can do it, because you did it in the literal next paragraph lmao.
He sat down at a spot where he could see the city from and took a deep breath, setting down his pocketwatch on the ground before starting to compare the landscape with the photograph.
Just add more detail here and you get a good "show" of Jonah feeling calm, instead of telling us that's how he feels. Stuff like "a warm feeling rose in his chest" or "he leaned back and smelled the fresh air as his gaze lingered on the city".
Adjust those two points, and you are on the road to be a certified chef.