>>44246
>So a simple bearing replacement might not be that simple because the bearing might not be the same sized it is used in contemporary bikes?

Everything is different. There are plenty of projects in net about modification of this bike, and most of them include lathe-made details and metal work, because modern (Chinese mostly) parts are different. That thing that I've disassembled called "bottom bracket" (I don't understand anything in bikes though, so may be wrong), and looks like it has design called "Thompson" that is officially rare (stated in Wiki), etc. Although I think I've had some similar old bearings somewhere, so maybe it would be easier.

>Does that bike use coaster brake (we call it "kontra" since it works when pedaling in contrary direction)?

Yes. It is old bike designed in USSR ("Salut", folding one), it has no gear shifting, steel frame (so it is 15kg full) and overall pretty simple. Picrelated of the mostly complete bike from internet.