Stains in bathroom and living room

Hello hello, I have been painting my house for 5 years. I noticed yellowish stains in the bathroom at the transition from wall to ceiling (see photo) and black stains in the living kitchen area above the refrigerator and oven (see photo). The second one is clearly soot, what kind of paint could be bought here? Anti-block paint. For example, against nicotine. As for the bathroom photo, I am worried about what it could be... poorly ventilated?

We have a spot that keeps reappearing (probably shale oil). We were recommended to use Sperrgrund there. That should work for you too, right?

Blocking agent? So first that and then paint?

yes

Exactly like that

What do you use for that? Just slap it onto fleece wallpapers?