How to remember English vocabularyies?  There is only one vocabulary in a language.  However there may be different KINDS of vocabulary for different aspects of the particular language.  For example, technical, business or legal usage.  As plural, it means words from different languages.

It is too difficult to remember so many words [or you can say, "...remember such a large vocabulary"] vocabularies. I think There are too many words we should need to learn.
In my mind,Some words looks very similar [Chinese have the same problem. eg 大太犬, 曰日, 由甲申 etc.  However, you have no problem with it] the same, and some words have different meanings [Same in Chinese, for example, 日 to mean sun or day]. For example, "affect" and "effect" looks almost the same but . Maybe the meanings are not is same.

How So difficult to remember they are!

Remembering is not difficult!  Forgetting is too easy.  You need to use the words often so that it stays in your mind.  Even as a native speaker, new words I learnt are soon forgotten if I don't use them for a few days!  So you see, your problem is not unique.  If you don't have the chance to use them, then create the chance.  So concentrate on the more common words and know how to use them properly before trying those difficult and rarely used ones.