what can I do in order to learn vocabulary ??( everyday 15 vocabulary )
It helps to begin with the most common words first.
Here is a good LINK for studying the 1000 most common words. You will see these over and over again.

Here is another list of 6000 words , in frequency order. The list is made by a computer, not by a person, so some of the "words" are contractions, inflected words, or parts of names that are not real words. (I'm is listed separately from I and am.) But this list has words ranked greater than 2000 linked to a dictionary entry.

Another way to increase vocabulary is to learn about roots, prefixes and suffixes. Here is a good LINK .

Another way to learn words is by reading. Select something that is a little bit above your level. If you choose something too easy, you will not learn anything new. If you choose something too difficult, you will be frustrated.

If you have questions on any vocabulary words, you can ask here.
I think, read more articles, watch more TVs