React redux code quality improvement

Hi Codecademy community, I’m relatively new to react and redux. I had to make an exam project where are I got the feedback that the code misses basic programming principles and there are too many code duplications. That is possibly true, the problem is that I can not see it.

Can any of you please advise how can I improve my code’s quality and what could be the basic programming principles which should be considered? Your answers, recommendations, links to information sources are highly appreciated.

The project can be found here.