Hello and welcome.

• yarn install to install packages;
• yarn start to run the application on /localhost:3000.

There are several things I have to mention:

• in channels' database there were two objects with identical keys. It turned out that Meubles channel had a wrong key. I fixed it.
• because of requirement do not use any other libraries I couldn't use any library to show real names of countries in dropdown; also I had to avoid using lodash, which has nice method range :) ;
• I deleted Search button, because I set searching channels function on every input change. I think it creates a simpler UX;
• I chose flex and wrap as a fast way to create responsible container, because there weren't any requirements about responsibility of a page. But if I had to do this, I suppose channels have to have a fixed size. So I would prefer to use @media on every column, so it would be five @media blocks.