not that long time ago I’ve read somewhere they are only (or mainly? Not sure now) in the arteries at heart. I don’t know how are they called in English.

One of the most common treatments is with statins. I think they basically work to dissolve the plaque. The easiest way is through diet and exercise though. As far as foods, look for stuff high in omega-3 like salmon, garlic, vitamin E and vitamin K. And I do think that it’s mostly in the arteries where plaque builds up.

First of all, statins inhibit biosynthesis of isoprenoid compounds in the body and thus should prevent formation of cholesterol by body (but you can still have high uptake from food). Second, it’s "omega 3-unsaturated fatty acids", omega-3 is nothing!

Hahaha oh my. The ways that I know that you can remove cholesterol, other than by blocking de novo cholesterol synthesis and absorbed cholesterol from animal sources in the diet, are invasive. They include taking a very small ballon and threading it through the arteries to a point where the thickening occurs and inflating it to push the plaques back. This does not remove but theoretically it could. The other way would be to literally scrape the vascular tissue from this inside out. Neither of these are done. Only the first part that I explained which is to push plaques back. The invasive ways can lead to pieces of plaque coming off leading to pulmonary embolism, cerebral strokes, and the well known heart attack.

I prefer the drugs and dietary intervention to invasive procedures.

As I understand it, materials are most likely to settle out on the inside of fast-flow curves, then get covered with clots that then build up more plaques. That happens mostly in arteries, build-up that can cause blockage would be more in small arteries, and blockage will more likely cause oxygen-deprivation effects in high-metabolism tissues like heart muscle and brain.