There is a secret to memorizing anything, words, names, addresses, telephone numbers, anything. You have to have a "hook" to hang that memory on. The strongest "hooks" are emotions. You may not remember every child in your first class at school. But everyone remembers the name of the first person they fell in love with. The secret to learning is to connect what you are learning with a picture in your head. The sillier a picture is, the easier it will be to remember.

I forgot to tell you. My husband is a genius. He was tested. He forgets many things. He cannot remember anyone's name until he has known them for some time.

Its totally normal when you don't use the language on a day to day basis you forget some of it.

Try to not memorize a lot of words in just one day it will be hard to keep them in your head go for like 10-30. and about forgetting peoples names I once had someone who i was having a conversation with to repeat his name like 4 or 5 times within half an hour and i forgot it every single time lol but when I do memorize a name I can recall it even after many years . 

using a word in a conversation without knowing how it sounds is a big mistake in many languages because some words sound completely different from what you might think they sound like.

just remember training makes Perfect :)

You reference an idea which is known as "eidetic memory." The notion of such memory is largely considered to be an urban myth. Unless you repeatedly use the four language skills of listening (with comprehension), reading, speaking, and writing, you will find yourself forgetting words you have memorized.

You must "use it or lose it." Although you may never lose 100% of what you previously learned, your skill will significantly degrade without practice. This is true of almost any type of learning, for example ability to play a musical instrument or sport with skill, as well as language, mathematics, etc.