This is a series that should help you understand how Czech grammatical cases work.
In this video, you can see the declensions of the word “žena” (a woman, wife), a model word for feminine nouns ending in -A (which is the most common ending for feminine nouns). You can observe that the core of the word stays the same, while the endings change. However, there are not 14 different endings (7 cases for singular and for plural), there are fewer. How many? Watch the video.
If you want a useful declensions handbook, you can buy my publication “Pocket Czech Declensions”.