Tips and notes for the Food 2 skill have an introduction to the adjective-noun agreement. Wikipedia and Read Ukrainian have more information on the subject. The resources also have a lot of useful information on other grammar topics. It is hard, I agree, but you don't have to learn the adjective-noun agreement for all cases at the beginning. If you do not do it 100% right, people will still understand you perfectly. BTW adverbs do not have an agreement.